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	$54.90	11.855%	$61.4084	$61.41	$61.40	$61.40
Purchase #2	$161.54	13.348%	$183.1024	$183.10	$183.10	$183.10
Purchase #3	$96.38	9.367%	$105.4079	$105.41	$105.40	$105.40
Purchase #4	$87.97	12.813%	$99.2416	$99.24	$99.25	$99.20
Purchase #5	$32.50	4.497%	$33.9615	$33.96	$33.95	$34.00
Purchase #6	$82.49	3.619%	$85.4753	$85.48	$85.50	$85.50
Purchase #7	$9.40	6.755%	$10.035	$10.04	$10.05	$10.00
7 purchase totals =	$525.18		$578.6321	$578.64	$578.65	$578.60