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	$181.79	5.521%	$191.8266	$191.83	$191.85	$191.80
Purchase #2	$96.56	3.817%	$100.2457	$100.25	$100.25	$100.20
Purchase #3	$220.79	4.738%	$231.251	$231.25	$231.25	$231.30
Purchase #4	$175.60	13.727%	$199.7046	$199.70	$199.70	$199.70
Purchase #5	$51.89	5.520%	$54.7543	$54.75	$54.75	$54.80
Purchase #6	$126.68	3.801%	$131.4951	$131.50	$131.50	$131.50
Purchase #7	$78.33	10.768%	$86.7646	$86.76	$86.75	$86.80
7 purchase totals =	$931.64		$996.0419	$996.04	$996.05	$996.10