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	$19.98	13.625%	$22.7023	$22.70	$22.70	$22.70
Purchase #2	$152.29	10.755%	$168.6688	$168.67	$168.65	$168.70
Purchase #3	$120.46	10.668%	$133.3107	$133.31	$133.30	$133.30
Purchase #4	$44.40	12.200%	$49.8168	$49.82	$49.80	$49.80
Purchase #5	$103.32	9.132%	$112.7552	$112.76	$112.75	$112.80
Purchase #6	$123.30	6.454%	$131.2578	$131.26	$131.25	$131.30
Purchase #7	$101.85	9.857%	$111.8894	$111.89	$111.90	$111.90
7 purchase totals =	$665.60		$730.4010	$730.41	$730.35	$730.50