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	$53.47	13.844%	$60.8724	$60.87	$60.85	$60.90
Purchase #2	$97.61	4.645%	$102.144	$102.14	$102.15	$102.10
Purchase #3	$118.99	7.298%	$127.6739	$127.67	$127.65	$127.70
Purchase #4	$220.51	11.505%	$245.8797	$245.88	$245.90	$245.90
Purchase #5	$53.68	3.766%	$55.7016	$55.70	$55.70	$55.70
Purchase #6	$192.78	9.288%	$210.6854	$210.69	$210.70	$210.70
Purchase #7	$79.59	3.764%	$82.5858	$82.59	$82.60	$82.60
7 purchase totals =	$816.63		$885.5428	$885.54	$885.55	$885.60