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	$248.99	5.590%	$262.9085	$262.91	$262.90	$262.90
Purchase #2	$206.44	9.286%	$225.61	$225.61	$225.60	$225.60
Purchase #3	$137.97	9.317%	$150.8247	$150.82	$150.80	$150.80
Purchase #4	$171.54	4.309%	$178.9317	$178.93	$178.95	$178.90
Purchase #5	$134.55	13.625%	$152.8824	$152.88	$152.90	$152.90
Purchase #6	$150.71	13.849%	$171.5818	$171.58	$171.60	$171.60
Purchase #7	$29.36	13.324%	$33.2719	$33.27	$33.25	$33.30
7 purchase totals =	$1,079.56		$1,176.0110	$1,176.00	$1,176.00	$1,176.00