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	$148.27	7.281%	$159.0655	$159.07	$159.05	$159.10
Purchase #2	$56.29	3.516%	$58.2692	$58.27	$58.25	$58.30
Purchase #3	$190.66	3.113%	$196.5952	$196.60	$196.60	$196.60
Purchase #4	$46.36	4.243%	$48.3271	$48.33	$48.35	$48.30
Purchase #5	$41.58	12.584%	$46.8124	$46.81	$46.80	$46.80
Purchase #6	$37.92	12.861%	$42.7969	$42.80	$42.80	$42.80
Purchase #7	$246.57	7.452%	$264.9444	$264.94	$264.95	$264.90
7 purchase totals =	$767.65		$816.8107	$816.82	$816.80	$816.80