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	$211.35	11.156%	$234.9282	$234.93	$234.95	$234.90
Purchase #2	$113.56	13.189%	$128.5374	$128.54	$128.55	$128.50
Purchase #3	$223.61	9.163%	$244.0994	$244.10	$244.10	$244.10
Purchase #4	$184.31	8.700%	$200.345	$200.35	$200.35	$200.30
Purchase #5	$70.28	12.141%	$78.8127	$78.81	$78.80	$78.80
Purchase #6	$145.81	13.443%	$165.4112	$165.41	$165.40	$165.40
Purchase #7	$148.35	11.144%	$164.8821	$164.88	$164.90	$164.90
7 purchase totals =	$1,097.27		$1,217.0160	$1,217.02	$1,217.05	$1,216.90