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	$187.45	3.705%	$194.395	$194.40	$194.40	$194.40
Purchase #2	$125.32	7.218%	$134.3656	$134.37	$134.35	$134.40
Purchase #3	$152.83	8.271%	$165.4706	$165.47	$165.45	$165.50
Purchase #4	$111.35	11.268%	$123.8969	$123.90	$123.90	$123.90
Purchase #5	$247.60	4.620%	$259.0391	$259.04	$259.05	$259.00
Purchase #6	$199.43	7.739%	$214.8639	$214.86	$214.85	$214.90
Purchase #7	$199.31	11.734%	$222.697	$222.70	$222.70	$222.70
7 purchase totals =	$1,223.29		$1,314.7281	$1,314.74	$1,314.70	$1,314.80