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	$104.60	3.414%	$108.171	$108.17	$108.15	$108.20
Purchase #2	$125.34	12.598%	$141.1303	$141.13	$141.15	$141.10
Purchase #3	$94.68	12.515%	$106.5292	$106.53	$106.55	$106.50
Purchase #4	$157.98	11.853%	$176.7054	$176.71	$176.70	$176.70
Purchase #5	$220.69	10.370%	$243.5756	$243.58	$243.60	$243.60
Purchase #6	$223.49	3.510%	$231.3345	$231.33	$231.35	$231.30
Purchase #7	$52.78	13.473%	$59.891	$59.89	$59.90	$59.90
7 purchase totals =	$979.56		$1,067.3370	$1,067.34	$1,067.40	$1,067.30