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	$192.50	10.410%	$212.5393	$212.54	$212.55	$212.50
Purchase #2	$131.87	9.767%	$144.7497	$144.75	$144.75	$144.70
Purchase #3	$90.72	4.561%	$94.8577	$94.86	$94.85	$94.90
Purchase #4	$236.65	7.409%	$254.1834	$254.18	$254.20	$254.20
Purchase #5	$40.33	7.625%	$43.4052	$43.41	$43.40	$43.40
Purchase #6	$89.76	9.439%	$98.2324	$98.23	$98.25	$98.20
Purchase #7	$216.31	6.573%	$230.5281	$230.53	$230.55	$230.50
7 purchase totals =	$998.14		$1,078.4958	$1,078.50	$1,078.55	$1,078.40