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	$111.57	12.412%	$125.4181	$125.42	$125.40	$125.40
Purchase #2	$80.82	5.700%	$85.4267	$85.43	$85.45	$85.40
Purchase #3	$184.48	13.626%	$209.6172	$209.62	$209.60	$209.60
Purchase #4	$109.36	13.354%	$123.9639	$123.96	$123.95	$124.00
Purchase #5	$207.40	6.266%	$220.3957	$220.40	$220.40	$220.40
Purchase #6	$180.57	5.835%	$191.1063	$191.11	$191.10	$191.10
Purchase #7	$74.25	10.805%	$82.2727	$82.27	$82.25	$82.30
7 purchase totals =	$948.45		$1,038.2006	$1,038.21	$1,038.15	$1,038.20