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	$119.63	4.510%	$125.0253	$125.03	$125.05	$125.00
Purchase #2	$72.59	8.297%	$78.6128	$78.61	$78.60	$78.60
Purchase #3	$127.68	9.375%	$139.65	$139.65	$139.65	$139.70
Purchase #4	$29.54	10.637%	$32.6822	$32.68	$32.70	$32.70
Purchase #5	$67.31	5.313%	$70.8862	$70.89	$70.90	$70.90
Purchase #6	$245.47	8.644%	$266.6884	$266.69	$266.70	$266.70
Purchase #7	$73.60	6.818%	$78.618	$78.62	$78.60	$78.60
7 purchase totals =	$735.82		$792.1629	$792.17	$792.20	$792.20