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	$212.68	7.811%	$229.2924	$229.29	$229.30	$229.30
Purchase #2	$117.51	4.693%	$123.0247	$123.02	$123.00	$123.00
Purchase #3	$151.61	9.203%	$165.5627	$165.56	$165.55	$165.60
Purchase #4	$91.61	13.197%	$103.6998	$103.70	$103.70	$103.70
Purchase #5	$91.53	8.805%	$99.5892	$99.59	$99.60	$99.60
Purchase #6	$181.82	7.262%	$195.0238	$195.02	$195.00	$195.00
Purchase #7	$17.97	3.487%	$18.5966	$18.60	$18.60	$18.60
7 purchase totals =	$864.73		$934.7892	$934.78	$934.75	$934.80