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	$173.31	10.312%	$191.1817	$191.18	$191.20	$191.20
Purchase #2	$81.39	8.138%	$88.0135	$88.01	$88.00	$88.00
Purchase #3	$10.32	11.123%	$11.4679	$11.47	$11.45	$11.50
Purchase #4	$128.82	10.549%	$142.4092	$142.41	$142.40	$142.40
Purchase #5	$132.29	10.674%	$146.4106	$146.41	$146.40	$146.40
Purchase #6	$65.91	6.111%	$69.9378	$69.94	$69.95	$69.90
Purchase #7	$131.90	11.436%	$146.9841	$146.98	$147.00	$147.00
7 purchase totals =	$723.94		$796.4048	$796.40	$796.40	$796.40