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	$191.73	7.270%	$205.6688	$205.67	$205.65	$205.70
Purchase #2	$40.64	4.805%	$42.5928	$42.59	$42.60	$42.60
Purchase #3	$122.90	10.677%	$136.022	$136.02	$136.00	$136.00
Purchase #4	$55.95	6.281%	$59.4642	$59.46	$59.45	$59.50
Purchase #5	$227.92	8.783%	$247.9382	$247.94	$247.95	$247.90
Purchase #6	$148.86	5.683%	$157.3197	$157.32	$157.30	$157.30
Purchase #7	$47.70	8.429%	$51.7206	$51.72	$51.70	$51.70
7 purchase totals =	$835.70		$900.7263	$900.72	$900.65	$900.70