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	$40.88	9.172%	$44.6295	$44.63	$44.65	$44.60
Purchase #2	$42.77	6.363%	$45.4915	$45.49	$45.50	$45.50
Purchase #3	$100.28	11.231%	$111.5424	$111.54	$111.55	$111.50
Purchase #4	$212.98	12.404%	$239.398	$239.40	$239.40	$239.40
Purchase #5	$104.88	4.304%	$109.394	$109.39	$109.40	$109.40
Purchase #6	$188.68	12.427%	$212.1273	$212.13	$212.15	$212.10
Purchase #7	$30.42	8.847%	$33.1113	$33.11	$33.10	$33.10
7 purchase totals =	$720.89		$795.6940	$795.69	$795.75	$795.60