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	$77.59	5.591%	$81.9281	$81.93	$81.95	$81.90
Purchase #2	$228.83	12.701%	$257.8937	$257.89	$257.90	$257.90
Purchase #3	$204.33	13.323%	$231.5529	$231.55	$231.55	$231.60
Purchase #4	$92.86	8.623%	$100.8673	$100.87	$100.85	$100.90
Purchase #5	$188.33	4.249%	$196.3321	$196.33	$196.35	$196.30
Purchase #6	$244.60	12.355%	$274.8203	$274.82	$274.80	$274.80
Purchase #7	$9.86	8.804%	$10.7281	$10.73	$10.75	$10.70
7 purchase totals =	$1,046.40		$1,154.1225	$1,154.12	$1,154.15	$1,154.10