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	$94.52	5.211%	$99.4454	$99.45	$99.45	$99.40
Purchase #2	$24.55	7.238%	$26.3269	$26.33	$26.35	$26.30
Purchase #3	$27.75	7.822%	$29.9206	$29.92	$29.90	$29.90
Purchase #4	$110.94	7.721%	$119.5057	$119.51	$119.50	$119.50
Purchase #5	$140.54	3.858%	$145.962	$145.96	$145.95	$146.00
Purchase #6	$245.38	11.628%	$273.9128	$273.91	$273.90	$273.90
Purchase #7	$132.50	3.853%	$137.6052	$137.61	$137.60	$137.60
7 purchase totals =	$776.18		$832.6786	$832.69	$832.65	$832.60