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	$128.63	13.411%	$145.8806	$145.88	$145.90	$145.90
Purchase #2	$233.54	13.519%	$265.1123	$265.11	$265.10	$265.10
Purchase #3	$53.94	13.537%	$61.2419	$61.24	$61.25	$61.20
Purchase #4	$112.87	13.597%	$128.2169	$128.22	$128.20	$128.20
Purchase #5	$77.48	10.863%	$85.8967	$85.90	$85.90	$85.90
Purchase #6	$236.57	9.253%	$258.4598	$258.46	$258.45	$258.50
Purchase #7	$245.81	11.449%	$273.9528	$273.95	$273.95	$274.00
7 purchase totals =	$1,088.84		$1,218.7610	$1,218.76	$1,218.75	$1,218.80