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	$184.33	6.468%	$196.2525	$196.25	$196.25	$196.30
Purchase #2	$164.48	12.745%	$185.443	$185.44	$185.45	$185.40
Purchase #3	$167.53	7.117%	$179.4531	$179.45	$179.45	$179.50
Purchase #4	$161.25	5.543%	$170.1881	$170.19	$170.20	$170.20
Purchase #5	$242.65	5.404%	$255.7628	$255.76	$255.75	$255.80
Purchase #6	$149.64	11.418%	$166.7259	$166.73	$166.75	$166.70
Purchase #7	$145.77	8.426%	$158.0526	$158.05	$158.05	$158.10
7 purchase totals =	$1,215.65		$1,311.8780	$1,311.87	$1,311.90	$1,312.00