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	$33.90	9.691%	$37.1852	$37.19	$37.20	$37.20
Purchase #2	$226.33	7.345%	$242.9539	$242.95	$242.95	$243.00
Purchase #3	$128.53	10.293%	$141.7596	$141.76	$141.75	$141.80
Purchase #4	$196.48	10.632%	$217.3698	$217.37	$217.35	$217.40
Purchase #5	$68.56	5.604%	$72.4021	$72.40	$72.40	$72.40
Purchase #6	$232.58	10.293%	$256.5195	$256.52	$256.50	$256.50
Purchase #7	$98.88	10.843%	$109.6016	$109.60	$109.60	$109.60
7 purchase totals =	$985.26		$1,077.7917	$1,077.79	$1,077.75	$1,077.90