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	$233.69	12.620%	$263.1817	$263.18	$263.20	$263.20
Purchase #2	$49.61	12.503%	$55.8127	$55.81	$55.80	$55.80
Purchase #3	$179.64	9.338%	$196.4148	$196.41	$196.40	$196.40
Purchase #4	$177.26	12.463%	$199.3519	$199.35	$199.35	$199.40
Purchase #5	$209.69	11.194%	$233.1627	$233.16	$233.15	$233.20
Purchase #6	$155.70	4.535%	$162.761	$162.76	$162.75	$162.80
Purchase #7	$18.75	4.850%	$19.6594	$19.66	$19.65	$19.70
7 purchase totals =	$1,024.34		$1,130.3442	$1,130.33	$1,130.30	$1,130.50