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	$231.77	13.281%	$262.5514	$262.55	$262.55	$262.60
Purchase #2	$128.32	13.745%	$145.9576	$145.96	$145.95	$146.00
Purchase #3	$44.71	9.362%	$48.8958	$48.90	$48.90	$48.90
Purchase #4	$239.59	7.821%	$258.3283	$258.33	$258.35	$258.30
Purchase #5	$141.71	11.559%	$158.0903	$158.09	$158.10	$158.10
Purchase #6	$98.28	4.177%	$102.3852	$102.39	$102.40	$102.40
Purchase #7	$63.76	5.319%	$67.1514	$67.15	$67.15	$67.20
7 purchase totals =	$948.14		$1,043.3600	$1,043.37	$1,043.40	$1,043.50