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	$18.53	4.472%	$19.3587	$19.36	$19.35	$19.40
Purchase #2	$230.55	5.470%	$243.1611	$243.16	$243.15	$243.20
Purchase #3	$227.94	12.501%	$256.4348	$256.43	$256.45	$256.40
Purchase #4	$44.50	9.710%	$48.821	$48.82	$48.80	$48.80
Purchase #5	$241.81	6.501%	$257.5301	$257.53	$257.55	$257.50
Purchase #6	$147.46	3.656%	$152.8511	$152.85	$152.85	$152.90
Purchase #7	$33.92	4.351%	$35.3959	$35.40	$35.40	$35.40
7 purchase totals =	$944.71		$1,013.5527	$1,013.55	$1,013.55	$1,013.60