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	$116.52	9.623%	$127.7327	$127.73	$127.75	$127.70
Purchase #2	$192.61	11.428%	$214.6215	$214.62	$214.60	$214.60
Purchase #3	$242.73	9.139%	$264.9131	$264.91	$264.90	$264.90
Purchase #4	$184.96	6.281%	$196.5773	$196.58	$196.60	$196.60
Purchase #5	$92.74	5.725%	$98.0494	$98.05	$98.05	$98.00
Purchase #6	$223.29	13.808%	$254.1219	$254.12	$254.10	$254.10
Purchase #7	$200.51	12.230%	$225.0324	$225.03	$225.05	$225.00
7 purchase totals =	$1,253.36		$1,381.0483	$1,381.04	$1,381.05	$1,380.90