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	$134.56	11.683%	$150.2806	$150.28	$150.30	$150.30
Purchase #2	$83.94	7.183%	$89.9694	$89.97	$89.95	$90.00
Purchase #3	$66.86	6.606%	$71.2768	$71.28	$71.30	$71.30
Purchase #4	$39.43	13.237%	$44.6493	$44.65	$44.65	$44.60
Purchase #5	$136.72	9.637%	$149.8957	$149.90	$149.90	$149.90
Purchase #6	$83.88	7.143%	$89.8715	$89.87	$89.85	$89.90
Purchase #7	$209.28	13.236%	$236.9803	$236.98	$237.00	$237.00
7 purchase totals =	$754.67		$832.9236	$832.93	$832.95	$833.00