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	$213.44	9.813%	$234.3849	$234.38	$234.40	$234.40
Purchase #2	$166.56	11.383%	$185.5195	$185.52	$185.50	$185.50
Purchase #3	$190.85	10.685%	$211.2423	$211.24	$211.25	$211.20
Purchase #4	$195.85	12.133%	$219.6125	$219.61	$219.60	$219.60
Purchase #5	$206.78	13.355%	$234.3955	$234.40	$234.40	$234.40
Purchase #6	$40.52	10.862%	$44.9213	$44.92	$44.90	$44.90
Purchase #7	$46.82	11.139%	$52.0353	$52.04	$52.05	$52.00
7 purchase totals =	$1,060.82		$1,182.1113	$1,182.11	$1,182.10	$1,182.00