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	$124.74	12.578%	$140.4298	$140.43	$140.45	$140.40
Purchase #2	$207.94	10.288%	$229.3329	$229.33	$229.35	$229.30
Purchase #3	$193.41	9.620%	$212.016	$212.02	$212.00	$212.00
Purchase #4	$55.63	6.367%	$59.172	$59.17	$59.15	$59.20
Purchase #5	$11.98	4.451%	$12.5132	$12.51	$12.50	$12.50
Purchase #6	$36.55	5.188%	$38.4462	$38.45	$38.45	$38.40
Purchase #7	$99.64	5.709%	$105.3284	$105.33	$105.35	$105.30
7 purchase totals =	$729.89		$797.2385	$797.24	$797.25	$797.10