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	$106.98	6.346%	$113.769	$113.77	$113.75	$113.80
Purchase #2	$62.53	12.395%	$70.2806	$70.28	$70.30	$70.30
Purchase #3	$39.91	3.758%	$41.4098	$41.41	$41.40	$41.40
Purchase #4	$52.37	4.677%	$54.8193	$54.82	$54.80	$54.80
Purchase #5	$240.94	4.167%	$250.98	$250.98	$251.00	$251.00
Purchase #6	$224.90	13.306%	$254.8252	$254.83	$254.85	$254.80
Purchase #7	$203.29	6.784%	$217.0812	$217.08	$217.10	$217.10
7 purchase totals =	$930.92		$1,003.1651	$1,003.17	$1,003.20	$1,003.20