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	$125.29	11.857%	$140.1456	$140.15	$140.15	$140.10
Purchase #2	$82.45	8.561%	$89.5085	$89.51	$89.50	$89.50
Purchase #3	$160.33	13.556%	$182.0643	$182.06	$182.05	$182.10
Purchase #4	$158.37	8.740%	$172.2115	$172.21	$172.20	$172.20
Purchase #5	$95.31	4.162%	$99.2768	$99.28	$99.30	$99.30
Purchase #6	$164.28	9.324%	$179.5975	$179.60	$179.60	$179.60
Purchase #7	$107.31	6.760%	$114.5642	$114.56	$114.55	$114.60
7 purchase totals =	$893.34		$977.3684	$977.37	$977.35	$977.40