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	$68.89	12.803%	$77.71	$77.71	$77.70	$77.70
Purchase #2	$151.26	5.872%	$160.142	$160.14	$160.15	$160.10
Purchase #3	$95.84	3.339%	$99.0401	$99.04	$99.05	$99.00
Purchase #4	$161.51	4.820%	$169.2948	$169.29	$169.30	$169.30
Purchase #5	$106.42	13.533%	$120.8218	$120.82	$120.80	$120.80
Purchase #6	$157.25	6.284%	$167.1316	$167.13	$167.15	$167.10
Purchase #7	$196.79	11.204%	$218.8384	$218.84	$218.85	$218.80
7 purchase totals =	$937.96		$1,012.9787	$1,012.97	$1,013.00	$1,012.80