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	$152.61	4.736%	$159.8376	$159.84	$159.85	$159.80
Purchase #2	$237.85	5.309%	$250.4775	$250.48	$250.50	$250.50
Purchase #3	$192.48	7.503%	$206.9218	$206.92	$206.90	$206.90
Purchase #4	$110.51	11.872%	$123.6297	$123.63	$123.65	$123.60
Purchase #5	$25.61	8.450%	$27.774	$27.77	$27.75	$27.80
Purchase #6	$192.55	13.343%	$218.2419	$218.24	$218.25	$218.20
Purchase #7	$184.49	7.771%	$198.8267	$198.83	$198.85	$198.80
7 purchase totals =	$1,096.10		$1,185.7092	$1,185.71	$1,185.75	$1,185.60