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	$125.73	13.295%	$142.4458	$142.45	$142.45	$142.40
Purchase #2	$100.72	13.242%	$114.0573	$114.06	$114.05	$114.10
Purchase #3	$102.60	11.709%	$114.6134	$114.61	$114.60	$114.60
Purchase #4	$116.86	7.753%	$125.9202	$125.92	$125.90	$125.90
Purchase #5	$80.49	12.295%	$90.3862	$90.39	$90.40	$90.40
Purchase #6	$141.84	9.199%	$154.8879	$154.89	$154.90	$154.90
Purchase #7	$121.88	4.201%	$127.0002	$127.00	$127.00	$127.00
7 purchase totals =	$790.12		$869.3110	$869.32	$869.30	$869.30