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	$68.32	4.636%	$71.4873	$71.49	$71.50	$71.50
Purchase #2	$62.71	3.556%	$64.94	$64.94	$64.95	$64.90
Purchase #3	$30.87	5.604%	$32.6	$32.60	$32.60	$32.60
Purchase #4	$229.34	6.445%	$244.121	$244.12	$244.10	$244.10
Purchase #5	$158.76	3.613%	$164.496	$164.50	$164.50	$164.50
Purchase #6	$118.77	8.108%	$128.3999	$128.40	$128.40	$128.40
Purchase #7	$27.89	3.448%	$28.8516	$28.85	$28.85	$28.90
7 purchase totals =	$696.66		$734.8958	$734.90	$734.90	$734.90