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	$229.89	4.754%	$240.819	$240.82	$240.80	$240.80
Purchase #2	$14.96	3.767%	$15.5235	$15.52	$15.50	$15.50
Purchase #3	$100.87	11.632%	$112.6032	$112.60	$112.60	$112.60
Purchase #4	$19.58	12.196%	$21.968	$21.97	$21.95	$22.00
Purchase #5	$226.56	10.335%	$249.975	$249.98	$250.00	$250.00
Purchase #6	$122.58	11.324%	$136.461	$136.46	$136.45	$136.50
Purchase #7	$98.76	10.847%	$109.4725	$109.47	$109.45	$109.50
7 purchase totals =	$813.20		$886.8222	$886.82	$886.75	$886.90