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	$186.81	5.376%	$196.8529	$196.85	$196.85	$196.90
Purchase #2	$37.28	13.295%	$42.2364	$42.24	$42.25	$42.20
Purchase #3	$175.85	8.409%	$190.6372	$190.64	$190.65	$190.60
Purchase #4	$66.32	6.399%	$70.5638	$70.56	$70.55	$70.60
Purchase #5	$81.57	9.123%	$89.0116	$89.01	$89.00	$89.00
Purchase #6	$181.66	13.131%	$205.5138	$205.51	$205.50	$205.50
Purchase #7	$37.75	3.851%	$39.2038	$39.20	$39.20	$39.20
7 purchase totals =	$767.24		$834.0195	$834.01	$834.00	$834.00