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	$184.73	4.246%	$192.5736	$192.57	$192.55	$192.60
Purchase #2	$180.68	8.776%	$196.5365	$196.54	$196.55	$196.50
Purchase #3	$156.58	9.285%	$171.1185	$171.12	$171.10	$171.10
Purchase #4	$95.36	13.698%	$108.4224	$108.42	$108.40	$108.40
Purchase #5	$144.89	10.144%	$159.5876	$159.59	$159.60	$159.60
Purchase #6	$118.57	11.429%	$132.1214	$132.12	$132.10	$132.10
Purchase #7	$45.91	10.190%	$50.5882	$50.59	$50.60	$50.60
7 purchase totals =	$926.72		$1,010.9482	$1,010.95	$1,010.90	$1,010.90