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	$159.46	10.170%	$175.6771	$175.68	$175.70	$175.70
Purchase #2	$33.76	11.720%	$37.7167	$37.72	$37.70	$37.70
Purchase #3	$88.32	6.682%	$94.2215	$94.22	$94.20	$94.20
Purchase #4	$57.63	9.128%	$62.8905	$62.89	$62.90	$62.90
Purchase #5	$76.79	12.508%	$86.3949	$86.39	$86.40	$86.40
Purchase #6	$134.56	10.346%	$148.4816	$148.48	$148.50	$148.50
Purchase #7	$167.32	12.649%	$188.4843	$188.48	$188.50	$188.50
7 purchase totals =	$717.84		$793.8666	$793.86	$793.90	$793.90