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	$143.25	13.109%	$162.0286	$162.03	$162.05	$162.00
Purchase #2	$42.90	8.324%	$46.471	$46.47	$46.45	$46.50
Purchase #3	$133.44	5.113%	$140.2628	$140.26	$140.25	$140.30
Purchase #4	$10.47	3.470%	$10.8333	$10.83	$10.85	$10.80
Purchase #5	$74.54	11.126%	$82.8333	$82.83	$82.85	$82.80
Purchase #6	$217.80	10.110%	$239.8196	$239.82	$239.80	$239.80
Purchase #7	$62.52	13.348%	$70.8652	$70.87	$70.85	$70.90
7 purchase totals =	$684.92		$753.1138	$753.11	$753.10	$753.10