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	$91.73	4.516%	$95.8725	$95.87	$95.85	$95.90
Purchase #2	$122.72	11.546%	$136.8893	$136.89	$136.90	$136.90
Purchase #3	$168.52	10.405%	$186.0545	$186.05	$186.05	$186.10
Purchase #4	$186.42	11.613%	$208.069	$208.07	$208.05	$208.10
Purchase #5	$7.73	6.515%	$8.2336	$8.23	$8.25	$8.20
Purchase #6	$203.50	10.219%	$224.2957	$224.30	$224.30	$224.30
Purchase #7	$56.85	4.507%	$59.4122	$59.41	$59.40	$59.40
7 purchase totals =	$837.47		$918.8268	$918.82	$918.80	$918.90