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	$72.37	13.666%	$82.2601	$82.26	$82.25	$82.30
Purchase #2	$126.48	4.282%	$131.8959	$131.90	$131.90	$131.90
Purchase #3	$26.90	12.568%	$30.2808	$30.28	$30.30	$30.30
Purchase #4	$237.74	7.343%	$255.1972	$255.20	$255.20	$255.20
Purchase #5	$174.64	13.593%	$198.3788	$198.38	$198.40	$198.40
Purchase #6	$176.96	8.360%	$191.7539	$191.75	$191.75	$191.80
Purchase #7	$57.56	3.363%	$59.4957	$59.50	$59.50	$59.50
7 purchase totals =	$872.65		$949.2624	$949.27	$949.30	$949.40