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	$230.48	6.657%	$245.8231	$245.82	$245.80	$245.80
Purchase #2	$138.46	4.289%	$144.3985	$144.40	$144.40	$144.40
Purchase #3	$229.61	7.644%	$247.1614	$247.16	$247.15	$247.20
Purchase #4	$28.66	11.866%	$32.0608	$32.06	$32.05	$32.10
Purchase #5	$191.72	7.186%	$205.497	$205.50	$205.50	$205.50
Purchase #6	$167.36	5.204%	$176.0694	$176.07	$176.05	$176.10
Purchase #7	$111.89	10.775%	$123.9461	$123.95	$123.95	$123.90
7 purchase totals =	$1,098.18		$1,174.9563	$1,174.96	$1,174.90	$1,175.00