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	$41.67	12.380%	$46.8287	$46.83	$46.85	$46.80
Purchase #2	$41.41	12.768%	$46.6972	$46.70	$46.70	$46.70
Purchase #3	$142.74	13.748%	$162.3639	$162.36	$162.35	$162.40
Purchase #4	$52.54	12.438%	$59.0749	$59.07	$59.05	$59.10
Purchase #5	$13.45	10.408%	$14.8499	$14.85	$14.85	$14.80
Purchase #6	$167.83	13.403%	$190.3243	$190.32	$190.30	$190.30
Purchase #7	$75.75	10.114%	$83.4114	$83.41	$83.40	$83.40
7 purchase totals =	$535.39		$603.5503	$603.54	$603.50	$603.50