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	$184.45	10.691%	$204.1695	$204.17	$204.15	$204.20
Purchase #2	$230.91	13.349%	$261.7342	$261.73	$261.75	$261.70
Purchase #3	$46.95	13.424%	$53.2526	$53.25	$53.25	$53.30
Purchase #4	$66.83	8.378%	$72.429	$72.43	$72.45	$72.40
Purchase #5	$79.40	13.844%	$90.3921	$90.39	$90.40	$90.40
Purchase #6	$200.65	7.449%	$215.5964	$215.60	$215.60	$215.60
Purchase #7	$45.57	7.381%	$48.9335	$48.93	$48.95	$48.90
7 purchase totals =	$854.76		$946.5073	$946.50	$946.55	$946.50