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	$198.69	13.520%	$225.5529	$225.55	$225.55	$225.60
Purchase #2	$79.40	12.220%	$89.1027	$89.10	$89.10	$89.10
Purchase #3	$86.87	8.560%	$94.3061	$94.31	$94.30	$94.30
Purchase #4	$67.33	6.636%	$71.798	$71.80	$71.80	$71.80
Purchase #5	$132.90	5.296%	$139.9384	$139.94	$139.95	$139.90
Purchase #6	$56.35	12.172%	$63.2089	$63.21	$63.20	$63.20
Purchase #7	$160.92	11.384%	$179.2391	$179.24	$179.25	$179.20
7 purchase totals =	$782.46		$863.1461	$863.15	$863.15	$863.10