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	$229.58	9.142%	$250.5682	$250.57	$250.55	$250.60
Purchase #2	$227.58	6.701%	$242.8301	$242.83	$242.85	$242.80
Purchase #3	$29.36	5.461%	$30.9633	$30.96	$30.95	$31.00
Purchase #4	$91.90	8.370%	$99.592	$99.59	$99.60	$99.60
Purchase #5	$50.52	9.476%	$55.3073	$55.31	$55.30	$55.30
Purchase #6	$222.72	6.381%	$236.9318	$236.93	$236.95	$236.90
Purchase #7	$84.85	3.205%	$87.5694	$87.57	$87.55	$87.60
7 purchase totals =	$936.51		$1,003.7621	$1,003.76	$1,003.75	$1,003.80