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	$131.83	10.532%	$145.7143	$145.71	$145.70	$145.70
Purchase #2	$40.31	8.276%	$43.6461	$43.65	$43.65	$43.60
Purchase #3	$176.55	4.821%	$185.0615	$185.06	$185.05	$185.10
Purchase #4	$201.59	6.676%	$215.0481	$215.05	$215.05	$215.00
Purchase #5	$147.54	12.516%	$166.0061	$166.01	$166.00	$166.00
Purchase #6	$189.25	7.733%	$203.8847	$203.88	$203.90	$203.90
Purchase #7	$187.59	11.495%	$209.1535	$209.15	$209.15	$209.20
7 purchase totals =	$1,074.66		$1,168.5143	$1,168.51	$1,168.50	$1,168.50