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	$94.45	4.138%	$98.3583	$98.36	$98.35	$98.40
Purchase #2	$41.94	6.230%	$44.5529	$44.55	$44.55	$44.60
Purchase #3	$51.29	11.415%	$57.1448	$57.14	$57.15	$57.10
Purchase #4	$115.62	10.131%	$127.3335	$127.33	$127.35	$127.30
Purchase #5	$125.61	13.228%	$142.2257	$142.23	$142.25	$142.20
Purchase #6	$125.31	12.284%	$140.7031	$140.70	$140.70	$140.70
Purchase #7	$137.45	4.698%	$143.9074	$143.91	$143.90	$143.90
7 purchase totals =	$691.67		$754.2257	$754.22	$754.25	$754.20