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	$177.44	12.671%	$199.9234	$199.92	$199.90	$199.90
Purchase #2	$228.37	7.146%	$244.6893	$244.69	$244.70	$244.70
Purchase #3	$50.85	10.677%	$56.2793	$56.28	$56.30	$56.30
Purchase #4	$157.55	7.773%	$169.7964	$169.80	$169.80	$169.80
Purchase #5	$187.82	4.503%	$196.2775	$196.28	$196.30	$196.30
Purchase #6	$95.59	10.626%	$105.7474	$105.75	$105.75	$105.70
Purchase #7	$150.30	5.727%	$158.9077	$158.91	$158.90	$158.90
7 purchase totals =	$1,047.92		$1,131.6210	$1,131.63	$1,131.65	$1,131.60