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	$149.50	11.841%	$167.2023	$167.20	$167.20	$167.20
Purchase #2	$199.34	13.306%	$225.8642	$225.86	$225.85	$225.90
Purchase #3	$127.95	9.119%	$139.6178	$139.62	$139.60	$139.60
Purchase #4	$165.87	9.573%	$181.7487	$181.75	$181.75	$181.70
Purchase #5	$62.71	12.404%	$70.4885	$70.49	$70.50	$70.50
Purchase #6	$54.90	7.828%	$59.1976	$59.20	$59.20	$59.20
Purchase #7	$168.48	4.241%	$175.6252	$175.63	$175.65	$175.60
7 purchase totals =	$928.75		$1,019.7443	$1,019.75	$1,019.75	$1,019.70