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	$46.38	6.850%	$49.557	$49.56	$49.55	$49.60
Purchase #2	$227.29	12.338%	$255.333	$255.33	$255.35	$255.30
Purchase #3	$217.82	5.782%	$230.4144	$230.41	$230.40	$230.40
Purchase #4	$102.73	3.683%	$106.5135	$106.51	$106.50	$106.50
Purchase #5	$148.81	11.432%	$165.822	$165.82	$165.80	$165.80
Purchase #6	$184.56	13.305%	$209.1157	$209.12	$209.10	$209.10
Purchase #7	$118.47	9.361%	$129.56	$129.56	$129.55	$129.60
7 purchase totals =	$1,046.06		$1,146.3156	$1,146.31	$1,146.25	$1,146.30