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	$94.95	4.431%	$99.1572	$99.16	$99.15	$99.20
Purchase #2	$80.29	12.796%	$90.5639	$90.56	$90.55	$90.60
Purchase #3	$176.70	11.278%	$196.6282	$196.63	$196.65	$196.60
Purchase #4	$78.31	7.248%	$83.9859	$83.99	$84.00	$84.00
Purchase #5	$67.35	12.523%	$75.7842	$75.78	$75.80	$75.80
Purchase #6	$202.72	10.252%	$223.5029	$223.50	$223.50	$223.50
Purchase #7	$249.36	7.116%	$267.1045	$267.10	$267.10	$267.10
7 purchase totals =	$949.68		$1,036.7268	$1,036.72	$1,036.75	$1,036.80