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	$204.27	12.293%	$229.3809	$229.38	$229.40	$229.40
Purchase #2	$16.91	6.116%	$17.9442	$17.94	$17.95	$17.90
Purchase #3	$202.67	12.814%	$228.6401	$228.64	$228.65	$228.60
Purchase #4	$220.55	3.607%	$228.5052	$228.51	$228.50	$228.50
Purchase #5	$86.72	4.403%	$90.5383	$90.54	$90.55	$90.50
Purchase #6	$105.98	4.261%	$110.4958	$110.50	$110.50	$110.50
Purchase #7	$215.68	13.834%	$245.5172	$245.52	$245.50	$245.50
7 purchase totals =	$1,052.78		$1,151.0217	$1,151.03	$1,151.05	$1,150.90