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	$123.92	4.715%	$129.7628	$129.76	$129.75	$129.80
Purchase #2	$30.38	5.830%	$32.1512	$32.15	$32.15	$32.20
Purchase #3	$61.26	9.440%	$67.0429	$67.04	$67.05	$67.00
Purchase #4	$84.28	6.570%	$89.8172	$89.82	$89.80	$89.80
Purchase #5	$191.91	3.725%	$199.0586	$199.06	$199.05	$199.10
Purchase #6	$200.71	11.841%	$224.4761	$224.48	$224.50	$224.50
Purchase #7	$121.70	10.339%	$134.2826	$134.28	$134.30	$134.30
7 purchase totals =	$814.16		$876.5914	$876.59	$876.60	$876.70