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	$196.73	3.145%	$202.9172	$202.92	$202.90	$202.90
Purchase #2	$240.27	4.258%	$250.5007	$250.50	$250.50	$250.50
Purchase #3	$250.45	8.572%	$271.9186	$271.92	$271.90	$271.90
Purchase #4	$163.77	4.484%	$171.1134	$171.11	$171.10	$171.10
Purchase #5	$153.30	7.660%	$165.0428	$165.04	$165.05	$165.00
Purchase #6	$101.74	7.795%	$109.6706	$109.67	$109.65	$109.70
Purchase #7	$159.47	5.709%	$168.5741	$168.57	$168.55	$168.60
7 purchase totals =	$1,265.73		$1,339.7374	$1,339.73	$1,339.65	$1,339.70