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	$206.84	4.825%	$216.82	$216.82	$216.80	$216.80
Purchase #2	$99.98	5.563%	$105.5419	$105.54	$105.55	$105.50
Purchase #3	$119.43	5.518%	$126.0201	$126.02	$126.00	$126.00
Purchase #4	$57.27	3.745%	$59.4148	$59.41	$59.40	$59.40
Purchase #5	$125.30	8.863%	$136.4053	$136.41	$136.40	$136.40
Purchase #6	$73.28	5.850%	$77.5669	$77.57	$77.55	$77.60
Purchase #7	$63.95	6.264%	$67.9558	$67.96	$67.95	$68.00
7 purchase totals =	$746.05		$789.7248	$789.73	$789.65	$789.70