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	$191.68	12.607%	$215.8451	$215.85	$215.85	$215.80
Purchase #2	$111.95	4.357%	$116.8277	$116.83	$116.85	$116.80
Purchase #3	$61.84	9.476%	$67.7	$67.70	$67.70	$67.70
Purchase #4	$109.69	10.485%	$121.191	$121.19	$121.20	$121.20
Purchase #5	$19.96	12.851%	$22.5251	$22.53	$22.55	$22.50
Purchase #6	$128.35	11.629%	$143.2758	$143.28	$143.30	$143.30
Purchase #7	$74.80	5.290%	$78.7569	$78.76	$78.75	$78.80
7 purchase totals =	$698.27		$766.1216	$766.14	$766.20	$766.10