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	$24.73	9.454%	$27.068	$27.07	$27.05	$27.10
Purchase #2	$71.82	9.388%	$78.5625	$78.56	$78.55	$78.60
Purchase #3	$25.43	6.500%	$27.083	$27.08	$27.10	$27.10
Purchase #4	$174.69	9.742%	$191.7083	$191.71	$191.70	$191.70
Purchase #5	$93.87	7.259%	$100.684	$100.68	$100.70	$100.70
Purchase #6	$29.89	7.335%	$32.0824	$32.08	$32.10	$32.10
Purchase #7	$154.80	7.801%	$166.8759	$166.88	$166.90	$166.90
7 purchase totals =	$575.23		$624.0641	$624.06	$624.10	$624.20