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	$239.50	5.602%	$252.9168	$252.92	$252.90	$252.90
Purchase #2	$55.37	8.119%	$59.8655	$59.87	$59.85	$59.90
Purchase #3	$146.86	6.731%	$156.7451	$156.75	$156.75	$156.70
Purchase #4	$152.54	5.760%	$161.3263	$161.33	$161.35	$161.30
Purchase #5	$83.97	4.185%	$87.4841	$87.48	$87.50	$87.50
Purchase #6	$174.47	13.639%	$198.266	$198.27	$198.25	$198.30
Purchase #7	$98.30	11.789%	$109.8886	$109.89	$109.90	$109.90
7 purchase totals =	$951.01		$1,026.4924	$1,026.51	$1,026.50	$1,026.50