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	$25.88	5.310%	$27.2542	$27.25	$27.25	$27.30
Purchase #2	$178.86	6.231%	$190.0048	$190.00	$190.00	$190.00
Purchase #3	$157.72	10.389%	$174.1055	$174.11	$174.10	$174.10
Purchase #4	$135.86	11.317%	$151.2353	$151.24	$151.25	$151.20
Purchase #5	$245.44	6.763%	$262.0391	$262.04	$262.05	$262.00
Purchase #6	$124.30	10.742%	$137.6523	$137.65	$137.65	$137.70
Purchase #7	$140.77	7.191%	$150.8928	$150.89	$150.90	$150.90
7 purchase totals =	$1,008.83		$1,093.1840	$1,093.18	$1,093.20	$1,093.20