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	$133.65	7.654%	$143.8796	$143.88	$143.90	$143.90
Purchase #2	$236.43	3.250%	$244.114	$244.11	$244.10	$244.10
Purchase #3	$135.58	5.387%	$142.8837	$142.88	$142.90	$142.90
Purchase #4	$110.31	10.259%	$121.6267	$121.63	$121.65	$121.60
Purchase #5	$138.88	4.850%	$145.6157	$145.62	$145.60	$145.60
Purchase #6	$147.46	6.362%	$156.8414	$156.84	$156.85	$156.80
Purchase #7	$95.48	10.452%	$105.4596	$105.46	$105.45	$105.50
7 purchase totals =	$997.79		$1,060.4207	$1,060.42	$1,060.45	$1,060.40