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	$219.69	10.813%	$243.4451	$243.45	$243.45	$243.40
Purchase #2	$196.47	6.436%	$209.1148	$209.11	$209.10	$209.10
Purchase #3	$244.55	12.641%	$275.4636	$275.46	$275.45	$275.50
Purchase #4	$30.31	13.737%	$34.4737	$34.47	$34.45	$34.50
Purchase #5	$209.48	5.432%	$220.859	$220.86	$220.85	$220.90
Purchase #6	$230.86	10.506%	$255.1142	$255.11	$255.10	$255.10
Purchase #7	$61.42	6.811%	$65.6033	$65.60	$65.60	$65.60
7 purchase totals =	$1,192.78		$1,304.0737	$1,304.06	$1,304.00	$1,304.10