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	$72.39	13.282%	$82.0048	$82.00	$82.00	$82.00
Purchase #2	$99.89	12.415%	$112.2913	$112.29	$112.30	$112.30
Purchase #3	$231.77	8.693%	$251.9178	$251.92	$251.90	$251.90
Purchase #4	$149.83	10.120%	$164.9928	$164.99	$165.00	$165.00
Purchase #5	$141.78	11.642%	$158.286	$158.29	$158.30	$158.30
Purchase #6	$94.34	11.663%	$105.3429	$105.34	$105.35	$105.30
Purchase #7	$154.86	4.358%	$161.6088	$161.61	$161.60	$161.60
7 purchase totals =	$944.86		$1,036.4444	$1,036.44	$1,036.45	$1,036.40