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	$126.58	8.849%	$137.7811	$137.78	$137.80	$137.80
Purchase #2	$91.89	9.559%	$100.6738	$100.67	$100.65	$100.70
Purchase #3	$93.60	7.663%	$100.7726	$100.77	$100.75	$100.80
Purchase #4	$35.49	4.104%	$36.9465	$36.95	$36.95	$36.90
Purchase #5	$17.91	3.671%	$18.5675	$18.57	$18.55	$18.60
Purchase #6	$154.56	5.385%	$162.8831	$162.88	$162.90	$162.90
Purchase #7	$206.39	3.486%	$213.5848	$213.58	$213.60	$213.60
7 purchase totals =	$726.42		$771.2094	$771.20	$771.20	$771.30