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	$151.79	11.212%	$168.8087	$168.81	$168.80	$168.80
Purchase #2	$117.82	11.203%	$131.0194	$131.02	$131.00	$131.00
Purchase #3	$140.38	3.689%	$145.5586	$145.56	$145.55	$145.60
Purchase #4	$116.45	6.726%	$124.2824	$124.28	$124.30	$124.30
Purchase #5	$216.27	11.356%	$240.8296	$240.83	$240.85	$240.80
Purchase #6	$95.26	5.475%	$100.4755	$100.48	$100.50	$100.50
Purchase #7	$66.30	6.319%	$70.4895	$70.49	$70.50	$70.50
7 purchase totals =	$904.27		$981.4637	$981.47	$981.50	$981.50