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	$33.31	3.127%	$34.3516	$34.35	$34.35	$34.40
Purchase #2	$91.33	8.773%	$99.3424	$99.34	$99.35	$99.30
Purchase #3	$42.88	10.120%	$47.2195	$47.22	$47.20	$47.20
Purchase #4	$85.75	8.308%	$92.8741	$92.87	$92.85	$92.90
Purchase #5	$41.72	4.803%	$43.7238	$43.72	$43.70	$43.70
Purchase #6	$12.37	13.369%	$14.0237	$14.02	$14.00	$14.00
Purchase #7	$208.97	11.491%	$232.9827	$232.98	$233.00	$233.00
7 purchase totals =	$516.33		$564.5178	$564.50	$564.45	$564.50