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	$77.94	11.427%	$86.8462	$86.85	$86.85	$86.80
Purchase #2	$75.58	4.443%	$78.938	$78.94	$78.95	$78.90
Purchase #3	$85.98	7.139%	$92.1181	$92.12	$92.10	$92.10
Purchase #4	$140.52	12.517%	$158.1089	$158.11	$158.10	$158.10
Purchase #5	$224.63	3.601%	$232.7189	$232.72	$232.70	$232.70
Purchase #6	$105.87	3.533%	$109.6104	$109.61	$109.60	$109.60
Purchase #7	$148.77	4.708%	$155.7741	$155.77	$155.75	$155.80
7 purchase totals =	$859.29		$914.1146	$914.12	$914.05	$914.00