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	$106.35	12.201%	$119.3258	$119.33	$119.35	$119.30
Purchase #2	$235.93	6.288%	$250.7653	$250.77	$250.75	$250.80
Purchase #3	$151.55	10.115%	$166.8793	$166.88	$166.90	$166.90
Purchase #4	$147.98	11.404%	$164.8556	$164.86	$164.85	$164.90
Purchase #5	$94.84	3.473%	$98.1338	$98.13	$98.15	$98.10
Purchase #6	$100.87	3.376%	$104.2754	$104.28	$104.30	$104.30
Purchase #7	$214.65	9.438%	$234.9087	$234.91	$234.90	$234.90
7 purchase totals =	$1,052.17		$1,139.1439	$1,139.16	$1,139.20	$1,139.20