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	$247.31	10.673%	$273.7054	$273.71	$273.70	$273.70
Purchase #2	$56.41	4.668%	$59.0432	$59.04	$59.05	$59.00
Purchase #3	$236.59	10.623%	$261.723	$261.72	$261.70	$261.70
Purchase #4	$218.80	7.721%	$235.6935	$235.69	$235.70	$235.70
Purchase #5	$31.96	9.435%	$34.9754	$34.98	$35.00	$35.00
Purchase #6	$175.53	11.660%	$195.9968	$196.00	$196.00	$196.00
Purchase #7	$30.33	10.106%	$33.3951	$33.40	$33.40	$33.40
7 purchase totals =	$996.93		$1,094.5324	$1,094.54	$1,094.55	$1,094.50