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	$188.81	10.716%	$209.0429	$209.04	$209.05	$209.00
Purchase #2	$116.96	11.501%	$130.4116	$130.41	$130.40	$130.40
Purchase #3	$34.73	13.826%	$39.5318	$39.53	$39.55	$39.50
Purchase #4	$223.40	6.836%	$238.6716	$238.67	$238.65	$238.70
Purchase #5	$219.34	5.690%	$231.8204	$231.82	$231.80	$231.80
Purchase #6	$58.48	12.268%	$65.6543	$65.65	$65.65	$65.70
Purchase #7	$96.87	7.217%	$103.8611	$103.86	$103.85	$103.90
7 purchase totals =	$938.59		$1,018.9937	$1,018.98	$1,018.95	$1,019.00