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	$123.57	3.471%	$127.8591	$127.86	$127.85	$127.90
Purchase #2	$150.57	6.755%	$160.741	$160.74	$160.75	$160.70
Purchase #3	$178.37	4.443%	$186.295	$186.30	$186.30	$186.30
Purchase #4	$79.91	7.313%	$85.7538	$85.75	$85.75	$85.80
Purchase #5	$37.55	8.727%	$40.827	$40.83	$40.85	$40.80
Purchase #6	$73.32	12.277%	$82.3215	$82.32	$82.30	$82.30
Purchase #7	$37.72	13.199%	$42.6987	$42.70	$42.70	$42.70
7 purchase totals =	$681.01		$726.4961	$726.50	$726.50	$726.50