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	$72.30	6.133%	$76.7342	$76.73	$76.75	$76.70
Purchase #2	$213.39	6.589%	$227.4503	$227.45	$227.45	$227.50
Purchase #3	$164.52	4.574%	$172.0451	$172.05	$172.05	$172.00
Purchase #4	$174.87	7.762%	$188.4434	$188.44	$188.45	$188.40
Purchase #5	$34.31	3.411%	$35.4803	$35.48	$35.50	$35.50
Purchase #6	$54.84	5.242%	$57.7147	$57.71	$57.70	$57.70
Purchase #7	$159.33	12.760%	$179.6605	$179.66	$179.65	$179.70
7 purchase totals =	$873.56		$937.5285	$937.52	$937.55	$937.50