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	$223.87	7.805%	$241.3431	$241.34	$241.35	$241.30
Purchase #2	$72.64	13.828%	$82.6847	$82.68	$82.70	$82.70
Purchase #3	$52.49	12.806%	$59.2119	$59.21	$59.20	$59.20
Purchase #4	$26.28	5.531%	$27.7335	$27.73	$27.75	$27.70
Purchase #5	$249.98	5.760%	$264.3788	$264.38	$264.40	$264.40
Purchase #6	$103.74	7.580%	$111.6035	$111.60	$111.60	$111.60
Purchase #7	$232.88	5.586%	$245.8887	$245.89	$245.90	$245.90
7 purchase totals =	$961.88		$1,032.8442	$1,032.83	$1,032.90	$1,032.80