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	$237.95	13.178%	$269.3071	$269.31	$269.30	$269.30
Purchase #2	$85.74	8.274%	$92.8341	$92.83	$92.85	$92.80
Purchase #3	$118.86	10.305%	$131.1085	$131.11	$131.10	$131.10
Purchase #4	$178.68	3.765%	$185.4073	$185.41	$185.40	$185.40
Purchase #5	$42.57	11.200%	$47.3378	$47.34	$47.35	$47.30
Purchase #6	$116.31	10.655%	$128.7028	$128.70	$128.70	$128.70
Purchase #7	$155.72	4.210%	$162.2758	$162.28	$162.30	$162.30
7 purchase totals =	$935.83		$1,016.9734	$1,016.98	$1,017.00	$1,016.90