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	$63.79	6.572%	$67.9823	$67.98	$68.00	$68.00
Purchase #2	$67.76	5.188%	$71.2754	$71.28	$71.30	$71.30
Purchase #3	$31.35	11.454%	$34.9408	$34.94	$34.95	$34.90
Purchase #4	$245.83	6.649%	$262.1752	$262.18	$262.20	$262.20
Purchase #5	$54.54	8.846%	$59.3646	$59.36	$59.35	$59.40
Purchase #6	$75.25	9.477%	$82.3814	$82.38	$82.40	$82.40
Purchase #7	$181.92	5.715%	$192.3167	$192.32	$192.30	$192.30
7 purchase totals =	$720.44		$770.4364	$770.44	$770.50	$770.50