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	$187.84	5.820%	$198.7723	$198.77	$198.75	$198.80
Purchase #2	$33.61	11.224%	$37.3824	$37.38	$37.40	$37.40
Purchase #3	$96.90	13.159%	$109.6511	$109.65	$109.65	$109.70
Purchase #4	$181.50	3.864%	$188.5132	$188.51	$188.50	$188.50
Purchase #5	$76.39	10.175%	$84.1627	$84.16	$84.15	$84.20
Purchase #6	$211.50	12.707%	$238.3753	$238.38	$238.40	$238.40
Purchase #7	$244.83	12.576%	$275.6198	$275.62	$275.60	$275.60
7 purchase totals =	$1,032.57		$1,132.4768	$1,132.47	$1,132.45	$1,132.60