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	$158.65	4.413%	$165.6512	$165.65	$165.65	$165.70
Purchase #2	$28.75	12.410%	$32.3179	$32.32	$32.30	$32.30
Purchase #3	$85.54	12.383%	$96.1324	$96.13	$96.15	$96.10
Purchase #4	$44.51	9.595%	$48.7807	$48.78	$48.80	$48.80
Purchase #5	$40.46	7.447%	$43.4731	$43.47	$43.45	$43.50
Purchase #6	$174.55	8.811%	$189.9296	$189.93	$189.95	$189.90
Purchase #7	$211.78	3.716%	$219.6497	$219.65	$219.65	$219.60
7 purchase totals =	$744.24		$795.9346	$795.93	$795.95	$795.90