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	$177.89	10.221%	$196.0721	$196.07	$196.05	$196.10
Purchase #2	$217.60	5.710%	$230.025	$230.03	$230.05	$230.00
Purchase #3	$233.56	4.336%	$243.6872	$243.69	$243.70	$243.70
Purchase #4	$102.62	12.660%	$115.6117	$115.61	$115.60	$115.60
Purchase #5	$92.52	3.598%	$95.8489	$95.85	$95.85	$95.80
Purchase #6	$191.37	12.434%	$215.1649	$215.16	$215.15	$215.20
Purchase #7	$18.96	6.529%	$20.1979	$20.20	$20.20	$20.20
7 purchase totals =	$1,034.52		$1,116.6077	$1,116.61	$1,116.60	$1,116.60