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	$10.86	4.330%	$11.3302	$11.33	$11.35	$11.30
Purchase #2	$105.49	3.824%	$109.5239	$109.52	$109.50	$109.50
Purchase #3	$125.34	9.157%	$136.8174	$136.82	$136.80	$136.80
Purchase #4	$233.52	11.461%	$260.2837	$260.28	$260.30	$260.30
Purchase #5	$134.25	4.535%	$140.3382	$140.34	$140.35	$140.30
Purchase #6	$134.83	13.187%	$152.61	$152.61	$152.60	$152.60
Purchase #7	$128.29	8.527%	$139.2293	$139.23	$139.25	$139.20
7 purchase totals =	$872.58		$950.1327	$950.13	$950.15	$950.00