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	$31.25	3.506%	$32.3456	$32.35	$32.35	$32.30
Purchase #2	$124.90	5.394%	$131.6371	$131.64	$131.65	$131.60
Purchase #3	$30.45	5.347%	$32.0782	$32.08	$32.10	$32.10
Purchase #4	$97.42	12.870%	$109.958	$109.96	$109.95	$110.00
Purchase #5	$151.92	11.828%	$169.8891	$169.89	$169.90	$169.90
Purchase #6	$102.72	13.285%	$116.3664	$116.37	$116.35	$116.40
Purchase #7	$42.49	4.282%	$44.3094	$44.31	$44.30	$44.30
7 purchase totals =	$581.15		$636.5838	$636.60	$636.60	$636.60