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	$52.29	4.274%	$54.5249	$54.52	$54.50	$54.50
Purchase #2	$52.55	5.380%	$55.3772	$55.38	$55.40	$55.40
Purchase #3	$144.56	13.500%	$164.0756	$164.08	$164.10	$164.10
Purchase #4	$238.57	6.814%	$254.8262	$254.83	$254.85	$254.80
Purchase #5	$64.32	6.765%	$68.6712	$68.67	$68.65	$68.70
Purchase #6	$230.90	5.198%	$242.9022	$242.90	$242.90	$242.90
Purchase #7	$117.46	11.307%	$130.7412	$130.74	$130.75	$130.70
7 purchase totals =	$900.65		$971.1185	$971.12	$971.15	$971.10