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	$143.91	3.273%	$148.6202	$148.62	$148.60	$148.60
Purchase #2	$164.93	10.813%	$182.7639	$182.76	$182.75	$182.80
Purchase #3	$85.25	11.582%	$95.1237	$95.12	$95.10	$95.10
Purchase #4	$144.75	9.141%	$157.9816	$157.98	$158.00	$158.00
Purchase #5	$154.68	9.816%	$169.8634	$169.86	$169.85	$169.90
Purchase #6	$244.74	4.735%	$256.3284	$256.33	$256.35	$256.30
Purchase #7	$37.31	8.804%	$40.5948	$40.59	$40.60	$40.60
7 purchase totals =	$975.57		$1,051.2760	$1,051.26	$1,051.25	$1,051.30