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	$55.40	6.622%	$59.0686	$59.07	$59.05	$59.10
Purchase #2	$44.42	7.760%	$47.867	$47.87	$47.85	$47.90
Purchase #3	$24.59	3.619%	$25.4799	$25.48	$25.50	$25.50
Purchase #4	$241.99	11.860%	$270.69	$270.69	$270.70	$270.70
Purchase #5	$156.72	11.188%	$174.2538	$174.25	$174.25	$174.30
Purchase #6	$38.45	4.827%	$40.306	$40.31	$40.30	$40.30
Purchase #7	$152.25	10.355%	$168.0155	$168.02	$168.00	$168.00
7 purchase totals =	$713.82		$785.6808	$785.69	$785.65	$785.80