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	$114.25	11.363%	$127.2322	$127.23	$127.25	$127.20
Purchase #2	$158.26	10.331%	$174.6098	$174.61	$174.60	$174.60
Purchase #3	$95.77	4.363%	$99.9484	$99.95	$99.95	$99.90
Purchase #4	$179.41	5.557%	$189.3798	$189.38	$189.40	$189.40
Purchase #5	$221.46	10.274%	$244.2128	$244.21	$244.20	$244.20
Purchase #6	$101.84	12.349%	$114.4162	$114.42	$114.40	$114.40
Purchase #7	$118.70	10.354%	$130.9902	$130.99	$131.00	$131.00
7 purchase totals =	$989.69		$1,080.7894	$1,080.79	$1,080.80	$1,080.70