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	$166.27	7.308%	$178.421	$178.42	$178.40	$178.40
Purchase #2	$153.26	13.498%	$173.947	$173.95	$173.95	$173.90
Purchase #3	$48.40	11.266%	$53.8527	$53.85	$53.85	$53.90
Purchase #4	$238.35	8.304%	$258.1426	$258.14	$258.15	$258.10
Purchase #5	$82.46	5.317%	$86.8444	$86.84	$86.85	$86.80
Purchase #6	$141.56	9.781%	$155.406	$155.41	$155.40	$155.40
Purchase #7	$123.62	12.537%	$139.1182	$139.12	$139.10	$139.10
7 purchase totals =	$953.92		$1,045.7319	$1,045.73	$1,045.70	$1,045.60