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	$16.27	11.511%	$18.1428	$18.14	$18.15	$18.10
Purchase #2	$151.52	11.636%	$169.1509	$169.15	$169.15	$169.20
Purchase #3	$206.58	6.747%	$220.518	$220.52	$220.50	$220.50
Purchase #4	$157.33	3.267%	$162.47	$162.47	$162.45	$162.50
Purchase #5	$188.50	8.775%	$205.0409	$205.04	$205.05	$205.00
Purchase #6	$230.35	3.678%	$238.8223	$238.82	$238.80	$238.80
Purchase #7	$101.38	7.827%	$109.315	$109.32	$109.30	$109.30
7 purchase totals =	$1,051.93		$1,123.4599	$1,123.46	$1,123.40	$1,123.40