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	$188.76	8.715%	$205.2104	$205.21	$205.20	$205.20
Purchase #2	$183.53	4.451%	$191.6989	$191.70	$191.70	$191.70
Purchase #3	$165.76	8.649%	$180.0966	$180.10	$180.10	$180.10
Purchase #4	$177.60	6.216%	$188.6396	$188.64	$188.65	$188.60
Purchase #5	$185.25	12.537%	$208.4748	$208.47	$208.45	$208.50
Purchase #6	$61.68	8.822%	$67.1214	$67.12	$67.10	$67.10
Purchase #7	$115.89	6.364%	$123.2652	$123.27	$123.25	$123.30
7 purchase totals =	$1,078.47		$1,164.5069	$1,164.51	$1,164.45	$1,164.50