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	$81.35	4.826%	$85.276	$85.28	$85.30	$85.30
Purchase #2	$149.80	11.449%	$166.9506	$166.95	$166.95	$167.00
Purchase #3	$86.85	3.310%	$89.7247	$89.72	$89.70	$89.70
Purchase #4	$31.89	11.846%	$35.6677	$35.67	$35.65	$35.70
Purchase #5	$80.72	5.742%	$85.3549	$85.35	$85.35	$85.40
Purchase #6	$10.78	10.760%	$11.9399	$11.94	$11.95	$11.90
Purchase #7	$115.82	13.845%	$131.8553	$131.86	$131.85	$131.90
7 purchase totals =	$557.21		$606.7691	$606.77	$606.75	$606.90