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	$245.36	6.851%	$262.1696	$262.17	$262.15	$262.20
Purchase #2	$39.96	7.370%	$42.9051	$42.91	$42.90	$42.90
Purchase #3	$30.25	7.799%	$32.6092	$32.61	$32.60	$32.60
Purchase #4	$218.80	13.140%	$247.5503	$247.55	$247.55	$247.60
Purchase #5	$123.62	10.146%	$136.1625	$136.16	$136.15	$136.20
Purchase #6	$177.93	11.312%	$198.0574	$198.06	$198.05	$198.10
Purchase #7	$169.55	5.130%	$178.2479	$178.25	$178.25	$178.20
7 purchase totals =	$1,005.47		$1,097.7020	$1,097.71	$1,097.65	$1,097.80