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	$209.58	5.820%	$221.7776	$221.78	$221.80	$221.80
Purchase #2	$185.81	6.772%	$198.3931	$198.39	$198.40	$198.40
Purchase #3	$60.31	9.239%	$65.882	$65.88	$65.90	$65.90
Purchase #4	$153.35	11.449%	$170.907	$170.91	$170.90	$170.90
Purchase #5	$241.70	10.585%	$267.2839	$267.28	$267.30	$267.30
Purchase #6	$140.66	7.594%	$151.3417	$151.34	$151.35	$151.30
Purchase #7	$95.47	4.564%	$99.8273	$99.83	$99.85	$99.80
7 purchase totals =	$1,086.88		$1,175.4126	$1,175.41	$1,175.50	$1,175.40