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	$167.44	8.831%	$182.2266	$182.23	$182.25	$182.20
Purchase #2	$56.69	8.589%	$61.5591	$61.56	$61.55	$61.60
Purchase #3	$146.29	9.783%	$160.6016	$160.60	$160.60	$160.60
Purchase #4	$150.52	6.221%	$159.8838	$159.88	$159.90	$159.90
Purchase #5	$50.71	4.346%	$52.9139	$52.91	$52.90	$52.90
Purchase #6	$234.69	7.673%	$252.6978	$252.70	$252.70	$252.70
Purchase #7	$137.49	5.810%	$145.4782	$145.48	$145.50	$145.50
7 purchase totals =	$943.83		$1,015.3610	$1,015.36	$1,015.40	$1,015.40