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	$171.95	11.136%	$191.0984	$191.10	$191.10	$191.10
Purchase #2	$152.52	12.700%	$171.89	$171.89	$171.90	$171.90
Purchase #3	$81.35	5.130%	$85.5233	$85.52	$85.50	$85.50
Purchase #4	$167.54	6.779%	$178.8975	$178.90	$178.90	$178.90
Purchase #5	$209.86	7.590%	$225.7884	$225.79	$225.80	$225.80
Purchase #6	$16.32	5.375%	$17.1972	$17.20	$17.20	$17.20
Purchase #7	$131.27	7.502%	$141.1179	$141.12	$141.10	$141.10
7 purchase totals =	$930.81		$1,011.5127	$1,011.52	$1,011.50	$1,011.50