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	$105.63	13.473%	$119.8615	$119.86	$119.85	$119.90
Purchase #2	$71.81	13.607%	$81.5812	$81.58	$81.60	$81.60
Purchase #3	$59.42	3.652%	$61.59	$61.59	$61.60	$61.60
Purchase #4	$64.96	8.528%	$70.4998	$70.50	$70.50	$70.50
Purchase #5	$83.90	9.851%	$92.165	$92.17	$92.15	$92.20
Purchase #6	$31.57	4.174%	$32.8877	$32.89	$32.90	$32.90
Purchase #7	$84.84	10.248%	$93.5344	$93.53	$93.55	$93.50
7 purchase totals =	$502.13		$552.1196	$552.12	$552.15	$552.20