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	$139.25	8.446%	$151.0111	$151.01	$151.00	$151.00
Purchase #2	$225.48	5.481%	$237.8386	$237.84	$237.85	$237.80
Purchase #3	$146.82	10.682%	$162.5033	$162.50	$162.50	$162.50
Purchase #4	$96.49	13.761%	$109.768	$109.77	$109.75	$109.80
Purchase #5	$29.97	4.371%	$31.28	$31.28	$31.30	$31.30
Purchase #6	$124.93	13.118%	$141.3183	$141.32	$141.30	$141.30
Purchase #7	$163.63	13.145%	$185.1392	$185.14	$185.15	$185.10
7 purchase totals =	$926.57		$1,018.8585	$1,018.86	$1,018.85	$1,018.80