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	$230.54	8.693%	$250.5808	$250.58	$250.60	$250.60
Purchase #2	$86.35	7.613%	$92.9238	$92.92	$92.90	$92.90
Purchase #3	$218.46	6.199%	$232.0023	$232.00	$232.00	$232.00
Purchase #4	$12.66	8.308%	$13.7118	$13.71	$13.70	$13.70
Purchase #5	$155.50	13.710%	$176.8191	$176.82	$176.80	$176.80
Purchase #6	$206.57	7.774%	$222.6288	$222.63	$222.65	$222.60
Purchase #7	$103.33	13.148%	$116.9158	$116.92	$116.90	$116.90
7 purchase totals =	$1,013.41		$1,105.5824	$1,105.58	$1,105.55	$1,105.50