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	$194.40	3.118%	$200.4614	$200.46	$200.45	$200.50
Purchase #2	$76.48	7.417%	$82.1525	$82.15	$82.15	$82.20
Purchase #3	$111.70	9.272%	$122.0568	$122.06	$122.05	$122.10
Purchase #4	$30.66	7.169%	$32.858	$32.86	$32.85	$32.90
Purchase #5	$41.51	4.859%	$43.527	$43.53	$43.55	$43.50
Purchase #6	$165.89	3.508%	$171.7094	$171.71	$171.70	$171.70
Purchase #7	$141.65	5.606%	$149.5909	$149.59	$149.60	$149.60
7 purchase totals =	$762.29		$802.3560	$802.36	$802.35	$802.50