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	$206.31	10.742%	$228.4718	$228.47	$228.45	$228.50
Purchase #2	$19.72	8.480%	$21.3923	$21.39	$21.40	$21.40
Purchase #3	$88.58	4.276%	$92.3677	$92.37	$92.35	$92.40
Purchase #4	$225.88	12.815%	$254.8265	$254.83	$254.85	$254.80
Purchase #5	$145.60	6.734%	$155.4047	$155.40	$155.40	$155.40
Purchase #6	$225.73	5.546%	$238.249	$238.25	$238.25	$238.20
Purchase #7	$11.81	4.454%	$12.336	$12.34	$12.35	$12.30
7 purchase totals =	$923.63		$1,003.0480	$1,003.05	$1,003.05	$1,003.00