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	$147.47	6.191%	$156.5999	$156.60	$156.60	$156.60
Purchase #2	$196.67	7.419%	$211.2609	$211.26	$211.25	$211.30
Purchase #3	$112.68	11.701%	$125.8647	$125.86	$125.85	$125.90
Purchase #4	$29.77	10.492%	$32.8935	$32.89	$32.90	$32.90
Purchase #5	$127.46	11.754%	$142.4416	$142.44	$142.45	$142.40
Purchase #6	$70.44	13.694%	$80.0861	$80.09	$80.10	$80.10
Purchase #7	$140.69	8.228%	$152.266	$152.27	$152.25	$152.30
7 purchase totals =	$825.18		$901.4127	$901.41	$901.40	$901.50