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	$144.32	12.478%	$162.3282	$162.33	$162.35	$162.30
Purchase #2	$84.51	7.185%	$90.582	$90.58	$90.60	$90.60
Purchase #3	$141.63	6.669%	$151.0753	$151.08	$151.10	$151.10
Purchase #4	$105.30	13.330%	$119.3365	$119.34	$119.35	$119.30
Purchase #5	$95.48	7.119%	$102.2772	$102.28	$102.30	$102.30
Purchase #6	$94.73	7.574%	$101.9049	$101.90	$101.90	$101.90
Purchase #7	$226.76	10.550%	$250.6832	$250.68	$250.70	$250.70
7 purchase totals =	$892.73		$978.1873	$978.19	$978.30	$978.20