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	$129.57	3.816%	$134.5144	$134.51	$134.50	$134.50
Purchase #2	$90.47	9.407%	$98.9805	$98.98	$99.00	$99.00
Purchase #3	$157.73	4.390%	$164.6543	$164.65	$164.65	$164.70
Purchase #4	$49.39	9.607%	$54.1349	$54.13	$54.15	$54.10
Purchase #5	$156.29	11.629%	$174.465	$174.47	$174.45	$174.50
Purchase #6	$149.52	11.674%	$166.975	$166.98	$167.00	$167.00
Purchase #7	$179.66	11.424%	$200.1844	$200.18	$200.20	$200.20
7 purchase totals =	$912.63		$993.9085	$993.90	$993.95	$994.00