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	$244.92	8.156%	$264.8957	$264.90	$264.90	$264.90
Purchase #2	$85.43	8.736%	$92.8932	$92.89	$92.90	$92.90
Purchase #3	$116.49	10.385%	$128.5875	$128.59	$128.60	$128.60
Purchase #4	$221.54	12.131%	$248.415	$248.42	$248.40	$248.40
Purchase #5	$221.27	3.697%	$229.4504	$229.45	$229.45	$229.50
Purchase #6	$5.58	6.695%	$5.9536	$5.95	$5.95	$6.00
Purchase #7	$78.43	9.630%	$85.9828	$85.98	$86.00	$86.00
7 purchase totals =	$973.66		$1,056.1782	$1,056.18	$1,056.20	$1,056.30