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	$105.33	7.312%	$113.0317	$113.03	$113.05	$113.00
Purchase #2	$37.80	13.208%	$42.7926	$42.79	$42.80	$42.80
Purchase #3	$82.49	8.706%	$89.6716	$89.67	$89.65	$89.70
Purchase #4	$24.53	13.450%	$27.8293	$27.83	$27.85	$27.80
Purchase #5	$217.31	5.817%	$229.9509	$229.95	$229.95	$230.00
Purchase #6	$36.77	5.819%	$38.9096	$38.91	$38.90	$38.90
Purchase #7	$31.51	12.811%	$35.5467	$35.55	$35.55	$35.50
7 purchase totals =	$535.74		$577.7324	$577.73	$577.75	$577.70