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	$184.82	6.249%	$196.3694	$196.37	$196.35	$196.40
Purchase #2	$42.96	8.461%	$46.5948	$46.59	$46.60	$46.60
Purchase #3	$113.31	6.179%	$120.3114	$120.31	$120.30	$120.30
Purchase #4	$168.60	13.373%	$191.1469	$191.15	$191.15	$191.10
Purchase #5	$203.99	8.698%	$221.7331	$221.73	$221.75	$221.70
Purchase #6	$141.61	9.168%	$154.5928	$154.59	$154.60	$154.60
Purchase #7	$33.46	11.834%	$37.4197	$37.42	$37.40	$37.40
7 purchase totals =	$888.75		$968.1681	$968.16	$968.15	$968.10