Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$133.26	7.304%	$142.9933	$142.99	$143.00	$143.00
Purchase #2	$127.77	7.451%	$137.2901	$137.29	$137.30	$137.30
Purchase #3	$216.86	11.700%	$242.2326	$242.23	$242.25	$242.20
Purchase #4	$111.60	8.218%	$120.7713	$120.77	$120.75	$120.80
Purchase #5	$191.83	13.263%	$217.2724	$217.27	$217.25	$217.30
Purchase #6	$120.68	5.511%	$127.3307	$127.33	$127.35	$127.30
Purchase #7	$130.87	10.288%	$144.3339	$144.33	$144.35	$144.30
7 purchase totals =	$1,032.87		$1,132.2243	$1,132.21	$1,132.25	$1,132.20