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	$157.65	6.346%	$167.6545	$167.65	$167.65	$167.70
Purchase #2	$155.82	5.807%	$164.8685	$164.87	$164.85	$164.90
Purchase #3	$119.69	9.717%	$131.3203	$131.32	$131.30	$131.30
Purchase #4	$218.52	5.276%	$230.0491	$230.05	$230.05	$230.00
Purchase #5	$180.34	11.737%	$201.5065	$201.51	$201.50	$201.50
Purchase #6	$134.52	5.479%	$141.8904	$141.89	$141.90	$141.90
Purchase #7	$95.77	4.251%	$99.8412	$99.84	$99.85	$99.80
7 purchase totals =	$1,062.31		$1,137.1305	$1,137.13	$1,137.10	$1,137.10