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	$221.75	5.332%	$233.5737	$233.57	$233.55	$233.60
Purchase #2	$91.91	8.769%	$99.9696	$99.97	$99.95	$100.00
Purchase #3	$132.62	8.588%	$144.0094	$144.01	$144.00	$144.00
Purchase #4	$233.57	11.805%	$261.1429	$261.14	$261.15	$261.10
Purchase #5	$173.65	12.532%	$195.4118	$195.41	$195.40	$195.40
Purchase #6	$59.80	4.114%	$62.2602	$62.26	$62.25	$62.30
Purchase #7	$124.73	5.216%	$131.2359	$131.24	$131.25	$131.20
7 purchase totals =	$1,038.03		$1,127.6035	$1,127.60	$1,127.55	$1,127.60