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	$56.67	5.738%	$59.9217	$59.92	$59.90	$59.90
Purchase #2	$132.32	5.597%	$139.726	$139.73	$139.75	$139.70
Purchase #3	$97.96	12.770%	$110.4695	$110.47	$110.45	$110.50
Purchase #4	$81.99	11.561%	$91.4689	$91.47	$91.45	$91.50
Purchase #5	$238.56	6.428%	$253.8946	$253.89	$253.90	$253.90
Purchase #6	$222.36	3.148%	$229.3599	$229.36	$229.35	$229.40
Purchase #7	$191.53	9.449%	$209.6277	$209.63	$209.65	$209.60
7 purchase totals =	$1,021.39		$1,094.4683	$1,094.47	$1,094.45	$1,094.50