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	$223.48	5.584%	$235.9591	$235.96	$235.95	$236.00
Purchase #2	$49.78	4.822%	$52.1804	$52.18	$52.20	$52.20
Purchase #3	$153.61	4.753%	$160.9111	$160.91	$160.90	$160.90
Purchase #4	$229.88	4.461%	$240.1349	$240.13	$240.15	$240.10
Purchase #5	$61.33	5.809%	$64.8927	$64.89	$64.90	$64.90
Purchase #6	$103.67	5.635%	$109.5118	$109.51	$109.50	$109.50
Purchase #7	$22.41	6.606%	$23.8904	$23.89	$23.90	$23.90
7 purchase totals =	$844.16		$887.4804	$887.47	$887.50	$887.50