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	$178.34	12.566%	$200.7502	$200.75	$200.75	$200.80
Purchase #2	$233.65	12.605%	$263.1016	$263.10	$263.10	$263.10
Purchase #3	$134.48	3.667%	$139.4114	$139.41	$139.40	$139.40
Purchase #4	$223.62	8.347%	$242.2856	$242.29	$242.30	$242.30
Purchase #5	$85.44	5.363%	$90.0221	$90.02	$90.00	$90.00
Purchase #6	$32.28	3.808%	$33.5092	$33.51	$33.50	$33.50
Purchase #7	$113.63	13.172%	$128.5973	$128.60	$128.60	$128.60
7 purchase totals =	$1,001.44		$1,097.6774	$1,097.68	$1,097.65	$1,097.70