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	$223.88	9.505%	$245.1598	$245.16	$245.15	$245.20
Purchase #2	$57.35	13.706%	$65.2104	$65.21	$65.20	$65.20
Purchase #3	$173.40	4.263%	$180.792	$180.79	$180.80	$180.80
Purchase #4	$130.64	6.618%	$139.2858	$139.29	$139.30	$139.30
Purchase #5	$95.83	3.805%	$99.4763	$99.48	$99.50	$99.50
Purchase #6	$132.61	4.577%	$138.6796	$138.68	$138.70	$138.70
Purchase #7	$238.88	4.716%	$250.1456	$250.15	$250.15	$250.10
7 purchase totals =	$1,052.59		$1,118.7495	$1,118.76	$1,118.80	$1,118.80