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	$155.66	4.524%	$162.7021	$162.70	$162.70	$162.70
Purchase #2	$113.40	6.768%	$121.0749	$121.07	$121.05	$121.10
Purchase #3	$144.73	12.194%	$162.3784	$162.38	$162.40	$162.40
Purchase #4	$228.56	6.637%	$243.7295	$243.73	$243.75	$243.70
Purchase #5	$218.43	5.215%	$229.8211	$229.82	$229.80	$229.80
Purchase #6	$72.82	7.675%	$78.4089	$78.41	$78.40	$78.40
Purchase #7	$132.67	13.137%	$150.0989	$150.10	$150.10	$150.10
7 purchase totals =	$1,066.27		$1,148.2138	$1,148.21	$1,148.20	$1,148.20