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	$123.26	3.359%	$127.4003	$127.40	$127.40	$127.40
Purchase #2	$195.31	9.344%	$213.5598	$213.56	$213.55	$213.60
Purchase #3	$25.67	12.726%	$28.9368	$28.94	$28.95	$28.90
Purchase #4	$34.32	9.784%	$37.6779	$37.68	$37.70	$37.70
Purchase #5	$69.73	12.826%	$78.6736	$78.67	$78.65	$78.70
Purchase #6	$149.34	12.858%	$168.5421	$168.54	$168.55	$168.50
Purchase #7	$104.85	12.799%	$118.2698	$118.27	$118.25	$118.30
7 purchase totals =	$702.48		$773.0603	$773.06	$773.05	$773.10