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	$227.36	4.487%	$237.5616	$237.56	$237.55	$237.60
Purchase #2	$173.28	10.205%	$190.9632	$190.96	$190.95	$191.00
Purchase #3	$10.94	5.618%	$11.5546	$11.55	$11.55	$11.60
Purchase #4	$39.86	5.581%	$42.0846	$42.08	$42.10	$42.10
Purchase #5	$197.67	11.618%	$220.6353	$220.64	$220.65	$220.60
Purchase #6	$179.78	9.395%	$196.6703	$196.67	$196.65	$196.70
Purchase #7	$131.93	3.321%	$136.3114	$136.31	$136.30	$136.30
7 purchase totals =	$960.82		$1,035.7810	$1,035.77	$1,035.75	$1,035.90