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	$80.69	11.443%	$89.9234	$89.92	$89.90	$89.90
Purchase #2	$51.55	11.149%	$57.2973	$57.30	$57.30	$57.30
Purchase #3	$90.80	4.576%	$94.955	$94.96	$94.95	$95.00
Purchase #4	$130.45	10.173%	$143.7207	$143.72	$143.70	$143.70
Purchase #5	$90.25	9.728%	$99.0295	$99.03	$99.05	$99.00
Purchase #6	$85.83	9.325%	$93.8336	$93.83	$93.85	$93.80
Purchase #7	$182.69	5.858%	$193.392	$193.39	$193.40	$193.40
7 purchase totals =	$712.26		$772.1515	$772.15	$772.15	$772.10