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	$110.78	11.375%	$123.3812	$123.38	$123.40	$123.40
Purchase #2	$241.78	11.642%	$269.928	$269.93	$269.95	$269.90
Purchase #3	$98.99	12.468%	$111.3321	$111.33	$111.35	$111.30
Purchase #4	$216.43	12.845%	$244.2304	$244.23	$244.25	$244.20
Purchase #5	$135.58	13.708%	$154.1653	$154.17	$154.15	$154.20
Purchase #6	$155.48	4.737%	$162.8451	$162.85	$162.85	$162.80
Purchase #7	$102.88	5.751%	$108.7966	$108.80	$108.80	$108.80
7 purchase totals =	$1,061.92		$1,174.6787	$1,174.69	$1,174.75	$1,174.60