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	$158.78	7.484%	$170.6631	$170.66	$170.65	$170.70
Purchase #2	$141.95	6.717%	$151.4848	$151.48	$151.50	$151.50
Purchase #3	$98.30	5.172%	$103.3841	$103.38	$103.40	$103.40
Purchase #4	$190.50	12.112%	$213.5734	$213.57	$213.55	$213.60
Purchase #5	$78.42	5.320%	$82.5919	$82.59	$82.60	$82.60
Purchase #6	$53.33	13.681%	$60.6261	$60.63	$60.65	$60.60
Purchase #7	$156.96	3.537%	$162.5117	$162.51	$162.50	$162.50
7 purchase totals =	$878.24		$944.8351	$944.82	$944.85	$944.90