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	$158.32	8.279%	$171.4273	$171.43	$171.45	$171.40
Purchase #2	$233.76	13.156%	$264.5135	$264.51	$264.50	$264.50
Purchase #3	$217.25	11.475%	$242.1794	$242.18	$242.20	$242.20
Purchase #4	$59.74	9.588%	$65.4679	$65.47	$65.45	$65.50
Purchase #5	$161.65	10.600%	$178.7849	$178.78	$178.80	$178.80
Purchase #6	$12.92	7.647%	$13.908	$13.91	$13.90	$13.90
Purchase #7	$159.80	6.184%	$169.682	$169.68	$169.70	$169.70
7 purchase totals =	$1,003.44		$1,105.9630	$1,105.96	$1,106.00	$1,106.00