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	$107.58	9.457%	$117.7538	$117.75	$117.75	$117.80
Purchase #2	$143.36	11.556%	$159.9267	$159.93	$159.95	$159.90
Purchase #3	$35.89	5.505%	$37.8657	$37.87	$37.85	$37.90
Purchase #4	$43.29	10.508%	$47.8389	$47.84	$47.85	$47.80
Purchase #5	$57.44	7.354%	$61.6641	$61.66	$61.65	$61.70
Purchase #6	$121.30	8.442%	$131.5401	$131.54	$131.55	$131.50
Purchase #7	$191.29	13.373%	$216.8712	$216.87	$216.85	$216.90
7 purchase totals =	$700.15		$773.4605	$773.46	$773.45	$773.50