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	$57.83	6.461%	$61.5664	$61.57	$61.55	$61.60
Purchase #2	$62.84	4.838%	$65.8802	$65.88	$65.90	$65.90
Purchase #3	$232.53	5.146%	$244.496	$244.50	$244.50	$244.50
Purchase #4	$143.31	11.839%	$160.2765	$160.28	$160.30	$160.30
Purchase #5	$185.54	13.535%	$210.6528	$210.65	$210.65	$210.70
Purchase #6	$163.91	13.864%	$186.6345	$186.63	$186.65	$186.60
Purchase #7	$108.32	7.747%	$116.7116	$116.71	$116.70	$116.70
7 purchase totals =	$954.28		$1,046.2180	$1,046.22	$1,046.25	$1,046.30