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	$114.94	3.199%	$118.6169	$118.62	$118.60	$118.60
Purchase #2	$183.47	7.215%	$196.7074	$196.71	$196.70	$196.70
Purchase #3	$33.87	12.855%	$38.224	$38.22	$38.20	$38.20
Purchase #4	$193.48	3.590%	$200.4259	$200.43	$200.45	$200.40
Purchase #5	$122.46	6.386%	$130.2803	$130.28	$130.30	$130.30
Purchase #6	$205.69	4.234%	$214.3989	$214.40	$214.40	$214.40
Purchase #7	$125.27	11.551%	$139.7399	$139.74	$139.75	$139.70
7 purchase totals =	$979.18		$1,038.3933	$1,038.40	$1,038.40	$1,038.30