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	$196.55	5.596%	$207.5489	$207.55	$207.55	$207.50
Purchase #2	$245.79	6.460%	$261.668	$261.67	$261.65	$261.70
Purchase #3	$64.59	11.759%	$72.1851	$72.19	$72.20	$72.20
Purchase #4	$129.52	10.789%	$143.4939	$143.49	$143.50	$143.50
Purchase #5	$140.41	8.600%	$152.4853	$152.49	$152.50	$152.50
Purchase #6	$243.84	12.150%	$273.4666	$273.47	$273.45	$273.50
Purchase #7	$108.88	13.160%	$123.2086	$123.21	$123.20	$123.20
7 purchase totals =	$1,129.58		$1,234.0564	$1,234.07	$1,234.05	$1,234.10