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	$67.55	7.572%	$72.6649	$72.66	$72.65	$72.70
Purchase #2	$82.83	3.106%	$85.4027	$85.40	$85.40	$85.40
Purchase #3	$123.38	6.620%	$131.5478	$131.55	$131.55	$131.50
Purchase #4	$149.64	10.710%	$165.6664	$165.67	$165.65	$165.70
Purchase #5	$184.95	10.716%	$204.7692	$204.77	$204.75	$204.80
Purchase #6	$191.83	12.786%	$216.3574	$216.36	$216.35	$216.40
Purchase #7	$100.70	9.715%	$110.483	$110.48	$110.50	$110.50
7 purchase totals =	$900.88		$986.8914	$986.89	$986.85	$987.00