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	$152.52	8.850%	$166.018	$166.02	$166.00	$166.00
Purchase #2	$167.55	11.874%	$187.4449	$187.44	$187.45	$187.40
Purchase #3	$109.93	8.523%	$119.2993	$119.30	$119.30	$119.30
Purchase #4	$143.53	5.346%	$151.2031	$151.20	$151.20	$151.20
Purchase #5	$52.33	7.341%	$56.1715	$56.17	$56.15	$56.20
Purchase #6	$133.25	3.484%	$137.8924	$137.89	$137.90	$137.90
Purchase #7	$247.54	11.498%	$276.0021	$276.00	$276.00	$276.00
7 purchase totals =	$1,006.65		$1,094.0313	$1,094.02	$1,094.00	$1,094.00