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	$112.72	6.264%	$119.7808	$119.78	$119.80	$119.80
Purchase #2	$51.73	9.723%	$56.7597	$56.76	$56.75	$56.80
Purchase #3	$167.40	8.460%	$181.562	$181.56	$181.55	$181.60
Purchase #4	$100.48	10.849%	$111.3811	$111.38	$111.40	$111.40
Purchase #5	$156.74	7.288%	$168.1632	$168.16	$168.15	$168.20
Purchase #6	$100.37	7.564%	$107.962	$107.96	$107.95	$108.00
Purchase #7	$101.27	5.175%	$106.5107	$106.51	$106.50	$106.50
7 purchase totals =	$790.71		$852.1195	$852.11	$852.10	$852.30