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	$72.51	6.835%	$77.4661	$77.47	$77.45	$77.50
Purchase #2	$85.46	3.750%	$88.6648	$88.66	$88.65	$88.70
Purchase #3	$48.56	6.327%	$51.6324	$51.63	$51.65	$51.60
Purchase #4	$35.26	11.778%	$39.4129	$39.41	$39.40	$39.40
Purchase #5	$98.41	7.596%	$105.8852	$105.89	$105.90	$105.90
Purchase #6	$45.42	13.143%	$51.3896	$51.39	$51.40	$51.40
Purchase #7	$175.79	13.668%	$199.817	$199.82	$199.80	$199.80
7 purchase totals =	$561.41		$614.2680	$614.27	$614.25	$614.30