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	$93.60	11.298%	$104.1749	$104.17	$104.15	$104.20
Purchase #2	$29.44	5.564%	$31.078	$31.08	$31.10	$31.10
Purchase #3	$119.74	7.147%	$128.2978	$128.30	$128.30	$128.30
Purchase #4	$38.91	12.872%	$43.9185	$43.92	$43.90	$43.90
Purchase #5	$44.80	12.661%	$50.4721	$50.47	$50.45	$50.50
Purchase #6	$49.43	9.415%	$54.0838	$54.08	$54.10	$54.10
Purchase #7	$37.79	4.513%	$39.4955	$39.50	$39.50	$39.50
7 purchase totals =	$413.71		$451.5206	$451.52	$451.50	$451.60