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	$155.37	7.502%	$167.0259	$167.03	$167.05	$167.00
Purchase #2	$150.38	5.650%	$158.8765	$158.88	$158.90	$158.90
Purchase #3	$229.92	13.554%	$261.0834	$261.08	$261.10	$261.10
Purchase #4	$169.90	5.528%	$179.2921	$179.29	$179.30	$179.30
Purchase #5	$33.93	4.810%	$35.562	$35.56	$35.55	$35.60
Purchase #6	$18.89	11.803%	$21.1196	$21.12	$21.10	$21.10
Purchase #7	$63.25	6.412%	$67.3056	$67.31	$67.30	$67.30
7 purchase totals =	$821.64		$890.2651	$890.27	$890.30	$890.30