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	$216.98	5.601%	$229.133	$229.13	$229.15	$229.10
Purchase #2	$126.46	4.330%	$131.9357	$131.94	$131.95	$131.90
Purchase #3	$30.95	7.139%	$33.1595	$33.16	$33.15	$33.20
Purchase #4	$95.92	10.808%	$106.287	$106.29	$106.30	$106.30
Purchase #5	$132.34	5.246%	$139.2826	$139.28	$139.30	$139.30
Purchase #6	$52.36	12.526%	$58.9186	$58.92	$58.90	$58.90
Purchase #7	$231.93	4.601%	$242.6011	$242.60	$242.60	$242.60
7 purchase totals =	$886.94		$941.3175	$941.32	$941.35	$941.30