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	$67.33	6.396%	$71.6364	$71.64	$71.65	$71.60
Purchase #2	$199.72	12.671%	$225.0265	$225.03	$225.05	$225.00
Purchase #3	$88.33	8.441%	$95.7859	$95.79	$95.80	$95.80
Purchase #4	$50.72	7.453%	$54.5002	$54.50	$54.50	$54.50
Purchase #5	$130.47	9.334%	$142.6481	$142.65	$142.65	$142.60
Purchase #6	$118.65	10.261%	$130.8247	$130.82	$130.80	$130.80
Purchase #7	$12.66	9.259%	$13.8322	$13.83	$13.85	$13.80
7 purchase totals =	$667.88		$734.2540	$734.26	$734.30	$734.10