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	$187.47	6.271%	$199.2262	$199.23	$199.25	$199.20
Purchase #2	$184.85	12.639%	$208.2132	$208.21	$208.20	$208.20
Purchase #3	$185.70	10.530%	$205.2542	$205.25	$205.25	$205.30
Purchase #4	$179.95	6.201%	$191.1087	$191.11	$191.10	$191.10
Purchase #5	$43.32	13.607%	$49.2146	$49.21	$49.20	$49.20
Purchase #6	$39.79	7.741%	$42.8701	$42.87	$42.85	$42.90
Purchase #7	$198.31	8.604%	$215.3726	$215.37	$215.35	$215.40
7 purchase totals =	$1,019.39		$1,111.2596	$1,111.25	$1,111.20	$1,111.30