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	$54.32	9.125%	$59.2767	$59.28	$59.30	$59.30
Purchase #2	$24.70	9.311%	$26.9998	$27.00	$27.00	$27.00
Purchase #3	$171.56	5.250%	$180.5669	$180.57	$180.55	$180.60
Purchase #4	$6.71	11.152%	$7.4583	$7.46	$7.45	$7.50
Purchase #5	$125.30	13.767%	$142.5501	$142.55	$142.55	$142.60
Purchase #6	$79.70	4.579%	$83.3495	$83.35	$83.35	$83.30
Purchase #7	$140.43	9.507%	$153.7807	$153.78	$153.80	$153.80
7 purchase totals =	$602.72		$653.9820	$653.99	$654.00	$654.10