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	$76.75	6.653%	$81.8562	$81.86	$81.85	$81.90
Purchase #2	$248.94	4.354%	$259.7788	$259.78	$259.80	$259.80
Purchase #3	$129.52	3.401%	$133.925	$133.93	$133.95	$133.90
Purchase #4	$83.69	7.290%	$89.791	$89.79	$89.80	$89.80
Purchase #5	$54.84	3.633%	$56.8323	$56.83	$56.85	$56.80
Purchase #6	$49.73	9.656%	$54.5319	$54.53	$54.55	$54.50
Purchase #7	$117.28	11.245%	$130.4681	$130.47	$130.45	$130.50
7 purchase totals =	$760.75		$807.1833	$807.19	$807.25	$807.20