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	$213.69	11.720%	$238.7345	$238.73	$238.75	$238.70
Purchase #2	$88.98	11.503%	$99.2154	$99.22	$99.20	$99.20
Purchase #3	$65.53	7.635%	$70.5332	$70.53	$70.55	$70.50
Purchase #4	$116.88	10.809%	$129.5136	$129.51	$129.50	$129.50
Purchase #5	$42.89	3.207%	$44.2655	$44.27	$44.25	$44.30
Purchase #6	$242.91	9.194%	$265.2431	$265.24	$265.25	$265.20
Purchase #7	$199.58	10.789%	$221.1127	$221.11	$221.10	$221.10
7 purchase totals =	$970.46		$1,068.6180	$1,068.61	$1,068.60	$1,068.50