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	$220.98	5.840%	$233.8852	$233.89	$233.90	$233.90
Purchase #2	$79.31	11.205%	$88.1967	$88.20	$88.20	$88.20
Purchase #3	$244.50	12.740%	$275.6493	$275.65	$275.65	$275.60
Purchase #4	$157.56	7.333%	$169.1139	$169.11	$169.10	$169.10
Purchase #5	$112.26	4.859%	$117.7147	$117.71	$117.70	$117.70
Purchase #6	$183.45	6.854%	$196.0237	$196.02	$196.00	$196.00
Purchase #7	$220.61	3.131%	$227.5173	$227.52	$227.50	$227.50
7 purchase totals =	$1,218.67		$1,308.1008	$1,308.10	$1,308.05	$1,308.00