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	$44.62	4.835%	$46.7774	$46.78	$46.80	$46.80
Purchase #2	$222.82	10.842%	$246.9781	$246.98	$247.00	$247.00
Purchase #3	$150.96	13.406%	$171.1977	$171.20	$171.20	$171.20
Purchase #4	$93.82	8.215%	$101.5273	$101.53	$101.55	$101.50
Purchase #5	$149.71	10.622%	$165.6122	$165.61	$165.60	$165.60
Purchase #6	$172.40	10.401%	$190.3313	$190.33	$190.35	$190.30
Purchase #7	$80.95	13.573%	$91.9373	$91.94	$91.95	$91.90
7 purchase totals =	$915.28		$1,014.3613	$1,014.37	$1,014.45	$1,014.30