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	$151.54	4.313%	$158.0759	$158.08	$158.10	$158.10
Purchase #2	$67.43	11.111%	$74.9221	$74.92	$74.90	$74.90
Purchase #3	$145.96	12.763%	$164.5889	$164.59	$164.60	$164.60
Purchase #4	$191.67	10.796%	$212.3627	$212.36	$212.35	$212.40
Purchase #5	$104.35	6.489%	$111.1213	$111.12	$111.10	$111.10
Purchase #6	$193.78	3.317%	$200.2077	$200.21	$200.20	$200.20
Purchase #7	$235.45	6.242%	$250.1468	$250.15	$250.15	$250.10
7 purchase totals =	$1,090.18		$1,171.4254	$1,171.43	$1,171.40	$1,171.40