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	$18.66	4.675%	$19.5324	$19.53	$19.55	$19.50
Purchase #2	$100.79	13.764%	$114.6627	$114.66	$114.65	$114.70
Purchase #3	$86.55	3.449%	$89.5351	$89.54	$89.55	$89.50
Purchase #4	$197.38	13.825%	$224.6678	$224.67	$224.65	$224.70
Purchase #5	$143.56	13.249%	$162.5803	$162.58	$162.60	$162.60
Purchase #6	$155.98	6.382%	$165.9346	$165.93	$165.95	$165.90
Purchase #7	$85.67	13.725%	$97.4282	$97.43	$97.45	$97.40
7 purchase totals =	$788.59		$874.3411	$874.34	$874.40	$874.30