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	$86.41	9.825%	$94.8998	$94.90	$94.90	$94.90
Purchase #2	$140.79	8.350%	$152.546	$152.55	$152.55	$152.50
Purchase #3	$191.72	13.107%	$216.8487	$216.85	$216.85	$216.80
Purchase #4	$153.56	4.508%	$160.4825	$160.48	$160.50	$160.50
Purchase #5	$112.53	5.790%	$119.0455	$119.05	$119.05	$119.00
Purchase #6	$221.40	11.773%	$247.4654	$247.47	$247.45	$247.50
Purchase #7	$87.89	9.514%	$96.2519	$96.25	$96.25	$96.30
7 purchase totals =	$994.30		$1,087.5398	$1,087.55	$1,087.55	$1,087.50