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	$72.52	3.668%	$75.18	$75.18	$75.20	$75.20
Purchase #2	$152.33	11.212%	$169.4092	$169.41	$169.40	$169.40
Purchase #3	$44.78	8.535%	$48.602	$48.60	$48.60	$48.60
Purchase #4	$45.46	6.433%	$48.3844	$48.38	$48.40	$48.40
Purchase #5	$55.31	7.637%	$59.534	$59.53	$59.55	$59.50
Purchase #6	$186.53	13.753%	$212.1835	$212.18	$212.20	$212.20
Purchase #7	$221.38	5.552%	$233.671	$233.67	$233.65	$233.70
7 purchase totals =	$778.31		$846.9641	$846.95	$847.00	$847.00