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	$146.95	4.376%	$153.3805	$153.38	$153.40	$153.40
Purchase #2	$197.91	6.379%	$210.5347	$210.53	$210.55	$210.50
Purchase #3	$240.82	6.176%	$255.693	$255.69	$255.70	$255.70
Purchase #4	$65.88	11.576%	$73.5063	$73.51	$73.50	$73.50
Purchase #5	$137.83	7.463%	$148.1163	$148.12	$148.10	$148.10
Purchase #6	$128.90	10.234%	$142.0916	$142.09	$142.10	$142.10
Purchase #7	$81.89	8.621%	$88.9497	$88.95	$88.95	$88.90
7 purchase totals =	$1,000.18		$1,072.2721	$1,072.27	$1,072.30	$1,072.20