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	$33.39	13.560%	$37.9177	$37.92	$37.90	$37.90
Purchase #2	$160.50	9.364%	$175.5292	$175.53	$175.55	$175.50
Purchase #3	$72.37	13.791%	$82.3505	$82.35	$82.35	$82.40
Purchase #4	$216.39	6.529%	$230.5181	$230.52	$230.50	$230.50
Purchase #5	$78.67	5.581%	$83.0606	$83.06	$83.05	$83.10
Purchase #6	$230.90	9.760%	$253.4358	$253.44	$253.45	$253.40
Purchase #7	$96.33	8.161%	$104.1915	$104.19	$104.20	$104.20
7 purchase totals =	$888.55		$967.0034	$967.01	$967.00	$967.00