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	$48.51	3.537%	$50.2258	$50.23	$50.25	$50.20
Purchase #2	$217.90	11.558%	$243.0849	$243.08	$243.10	$243.10
Purchase #3	$242.80	6.871%	$259.4828	$259.48	$259.50	$259.50
Purchase #4	$104.42	9.394%	$114.2292	$114.23	$114.25	$114.20
Purchase #5	$55.98	6.814%	$59.7945	$59.79	$59.80	$59.80
Purchase #6	$177.99	12.528%	$200.2886	$200.29	$200.30	$200.30
Purchase #7	$111.78	7.844%	$120.548	$120.55	$120.55	$120.50
7 purchase totals =	$959.38		$1,047.6538	$1,047.65	$1,047.75	$1,047.60