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	$56.46	9.105%	$61.6007	$61.60	$61.60	$61.60
Purchase #2	$165.86	4.827%	$173.8661	$173.87	$173.85	$173.90
Purchase #3	$233.86	12.162%	$262.3021	$262.30	$262.30	$262.30
Purchase #4	$221.60	11.399%	$246.8602	$246.86	$246.85	$246.90
Purchase #5	$74.78	12.212%	$83.9121	$83.91	$83.90	$83.90
Purchase #6	$39.34	13.673%	$44.719	$44.72	$44.70	$44.70
Purchase #7	$99.96	12.323%	$112.2781	$112.28	$112.30	$112.30
7 purchase totals =	$891.86		$985.5383	$985.54	$985.50	$985.60