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	$85.90	4.121%	$89.4399	$89.44	$89.45	$89.40
Purchase #2	$113.89	5.735%	$120.4216	$120.42	$120.40	$120.40
Purchase #3	$76.77	5.601%	$81.0699	$81.07	$81.05	$81.10
Purchase #4	$10.69	7.175%	$11.457	$11.46	$11.45	$11.50
Purchase #5	$195.25	4.416%	$203.8722	$203.87	$203.85	$203.90
Purchase #6	$172.65	3.367%	$178.4631	$178.46	$178.45	$178.50
Purchase #7	$159.63	4.580%	$166.9411	$166.94	$166.95	$166.90
7 purchase totals =	$814.78		$851.6648	$851.66	$851.60	$851.70