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	$204.70	3.770%	$212.4172	$212.42	$212.40	$212.40
Purchase #2	$92.96	9.242%	$101.5514	$101.55	$101.55	$101.60
Purchase #3	$57.37	4.360%	$59.8713	$59.87	$59.85	$59.90
Purchase #4	$97.98	10.794%	$108.556	$108.56	$108.55	$108.60
Purchase #5	$90.67	10.471%	$100.1641	$100.16	$100.15	$100.20
Purchase #6	$215.49	13.390%	$244.3441	$244.34	$244.35	$244.30
Purchase #7	$249.50	12.133%	$279.7718	$279.77	$279.75	$279.80
7 purchase totals =	$1,008.67		$1,106.6759	$1,106.67	$1,106.60	$1,106.80