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	$185.58	6.104%	$196.9078	$196.91	$196.90	$196.90
Purchase #2	$14.88	8.181%	$16.0973	$16.10	$16.10	$16.10
Purchase #3	$5.32	10.662%	$5.8872	$5.89	$5.90	$5.90
Purchase #4	$124.32	6.211%	$132.0415	$132.04	$132.05	$132.00
Purchase #5	$41.43	3.499%	$42.8796	$42.88	$42.90	$42.90
Purchase #6	$79.82	9.151%	$87.1243	$87.12	$87.10	$87.10
Purchase #7	$159.66	5.163%	$167.9032	$167.90	$167.90	$167.90
7 purchase totals =	$611.01		$648.8409	$648.84	$648.85	$648.80