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	$30.72	5.588%	$32.4366	$32.44	$32.45	$32.40
Purchase #2	$105.81	6.568%	$112.7596	$112.76	$112.75	$112.80
Purchase #3	$90.80	6.581%	$96.7755	$96.78	$96.80	$96.80
Purchase #4	$79.53	4.776%	$83.3284	$83.33	$83.35	$83.30
Purchase #5	$154.77	13.441%	$175.5726	$175.57	$175.55	$175.60
Purchase #6	$119.81	10.640%	$132.5578	$132.56	$132.55	$132.60
Purchase #7	$108.28	10.428%	$119.5714	$119.57	$119.55	$119.60
7 purchase totals =	$689.72		$753.0019	$753.01	$753.00	$753.10