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	$144.52	11.138%	$160.6166	$160.62	$160.60	$160.60
Purchase #2	$165.64	6.520%	$176.4397	$176.44	$176.45	$176.40
Purchase #3	$64.28	12.638%	$72.4037	$72.40	$72.40	$72.40
Purchase #4	$169.77	9.443%	$185.8014	$185.80	$185.80	$185.80
Purchase #5	$236.52	7.343%	$253.8877	$253.89	$253.90	$253.90
Purchase #6	$231.53	12.830%	$261.2353	$261.24	$261.25	$261.20
Purchase #7	$67.55	10.792%	$74.84	$74.84	$74.85	$74.80
7 purchase totals =	$1,079.81		$1,185.2244	$1,185.23	$1,185.25	$1,185.10