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	$110.52	3.747%	$114.6612	$114.66	$114.65	$114.70
Purchase #2	$100.77	10.751%	$111.6038	$111.60	$111.60	$111.60
Purchase #3	$55.64	11.286%	$61.9195	$61.92	$61.90	$61.90
Purchase #4	$207.86	12.545%	$233.936	$233.94	$233.95	$233.90
Purchase #5	$203.34	3.767%	$210.9998	$211.00	$211.00	$211.00
Purchase #6	$129.92	8.323%	$140.7332	$140.73	$140.75	$140.70
Purchase #7	$137.51	7.339%	$147.6019	$147.60	$147.60	$147.60
7 purchase totals =	$945.56		$1,021.4554	$1,021.45	$1,021.45	$1,021.40