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	$121.63	4.638%	$127.2712	$127.27	$127.25	$127.30
Purchase #2	$69.79	11.369%	$77.7244	$77.72	$77.70	$77.70
Purchase #3	$79.77	10.386%	$88.0549	$88.05	$88.05	$88.10
Purchase #4	$244.59	6.123%	$259.5662	$259.57	$259.55	$259.60
Purchase #5	$86.44	10.670%	$95.6631	$95.66	$95.65	$95.70
Purchase #6	$108.30	3.699%	$112.306	$112.31	$112.30	$112.30
Purchase #7	$118.83	11.200%	$132.139	$132.14	$132.15	$132.10
7 purchase totals =	$829.35		$892.7248	$892.72	$892.65	$892.80