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	$164.59	12.494%	$185.1539	$185.15	$185.15	$185.20
Purchase #2	$37.90	6.467%	$40.351	$40.35	$40.35	$40.40
Purchase #3	$212.70	11.718%	$237.6242	$237.62	$237.60	$237.60
Purchase #4	$206.89	11.517%	$230.7175	$230.72	$230.70	$230.70
Purchase #5	$174.75	12.463%	$196.5291	$196.53	$196.55	$196.50
Purchase #6	$157.92	10.666%	$174.7637	$174.76	$174.75	$174.80
Purchase #7	$192.94	13.319%	$218.6377	$218.64	$218.65	$218.60
7 purchase totals =	$1,147.69		$1,283.7771	$1,283.77	$1,283.75	$1,283.80