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	$153.72	7.215%	$164.8109	$164.81	$164.80	$164.80
Purchase #2	$76.88	10.720%	$85.1215	$85.12	$85.10	$85.10
Purchase #3	$53.53	11.313%	$59.5858	$59.59	$59.60	$59.60
Purchase #4	$8.66	12.400%	$9.7338	$9.73	$9.75	$9.70
Purchase #5	$19.57	12.436%	$22.0037	$22.00	$22.00	$22.00
Purchase #6	$189.64	3.563%	$196.3969	$196.40	$196.40	$196.40
Purchase #7	$17.46	3.650%	$18.0973	$18.10	$18.10	$18.10
7 purchase totals =	$519.46		$555.7499	$555.75	$555.75	$555.70