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	$54.64	3.193%	$56.3847	$56.38	$56.40	$56.40
Purchase #2	$10.46	3.873%	$10.8651	$10.87	$10.85	$10.90
Purchase #3	$119.33	9.456%	$130.6138	$130.61	$130.60	$130.60
Purchase #4	$233.41	3.846%	$242.3869	$242.39	$242.40	$242.40
Purchase #5	$140.91	8.767%	$153.2636	$153.26	$153.25	$153.30
Purchase #6	$65.91	9.247%	$72.0047	$72.00	$72.00	$72.00
Purchase #7	$250.82	5.307%	$264.131	$264.13	$264.15	$264.10
7 purchase totals =	$875.48		$929.6498	$929.64	$929.65	$929.70