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	$191.29	8.329%	$207.2225	$207.22	$207.20	$207.20
Purchase #2	$38.64	11.586%	$43.1168	$43.12	$43.10	$43.10
Purchase #3	$94.58	9.460%	$103.5273	$103.53	$103.55	$103.50
Purchase #4	$201.50	10.444%	$222.5447	$222.54	$222.55	$222.50
Purchase #5	$137.95	10.375%	$152.2623	$152.26	$152.25	$152.30
Purchase #6	$95.32	5.318%	$100.3891	$100.39	$100.40	$100.40
Purchase #7	$187.59	6.202%	$199.2243	$199.22	$199.20	$199.20
7 purchase totals =	$946.87		$1,028.2870	$1,028.28	$1,028.25	$1,028.20