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	$22.53	3.670%	$23.3569	$23.36	$23.35	$23.40
Purchase #2	$214.63	3.384%	$221.8931	$221.89	$221.90	$221.90
Purchase #3	$40.83	12.565%	$45.9603	$45.96	$45.95	$46.00
Purchase #4	$232.37	11.759%	$259.6944	$259.69	$259.70	$259.70
Purchase #5	$73.84	11.817%	$82.5657	$82.57	$82.55	$82.60
Purchase #6	$215.98	10.510%	$238.6795	$238.68	$238.70	$238.70
Purchase #7	$107.68	3.637%	$111.5963	$111.60	$111.60	$111.60
7 purchase totals =	$907.86		$983.7462	$983.75	$983.75	$983.90