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	$40.32	6.793%	$43.0589	$43.06	$43.05	$43.10
Purchase #2	$172.51	10.870%	$191.2618	$191.26	$191.25	$191.30
Purchase #3	$195.96	13.652%	$222.7125	$222.71	$222.70	$222.70
Purchase #4	$191.69	7.590%	$206.2393	$206.24	$206.25	$206.20
Purchase #5	$221.29	10.320%	$244.1271	$244.13	$244.15	$244.10
Purchase #6	$103.37	9.801%	$113.5013	$113.50	$113.50	$113.50
Purchase #7	$73.33	9.795%	$80.5127	$80.51	$80.50	$80.50
7 purchase totals =	$998.47		$1,101.4136	$1,101.41	$1,101.40	$1,101.40