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	$34.89	7.555%	$37.5259	$37.53	$37.55	$37.50
Purchase #2	$91.74	9.858%	$100.7837	$100.78	$100.80	$100.80
Purchase #3	$91.87	6.194%	$97.5604	$97.56	$97.55	$97.60
Purchase #4	$249.97	5.445%	$263.5809	$263.58	$263.60	$263.60
Purchase #5	$245.93	12.413%	$276.4573	$276.46	$276.45	$276.50
Purchase #6	$140.88	7.572%	$151.5474	$151.55	$151.55	$151.50
Purchase #7	$135.78	4.581%	$142.0001	$142.00	$142.00	$142.00
7 purchase totals =	$991.06		$1,069.4557	$1,069.46	$1,069.50	$1,069.50