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	$165.30	12.502%	$185.9658	$185.97	$185.95	$186.00
Purchase #2	$82.79	13.482%	$93.9517	$93.95	$93.95	$94.00
Purchase #3	$96.71	6.757%	$103.2447	$103.24	$103.25	$103.20
Purchase #4	$86.61	3.665%	$89.7843	$89.78	$89.80	$89.80
Purchase #5	$199.96	8.615%	$217.1866	$217.19	$217.20	$217.20
Purchase #6	$126.55	4.211%	$131.879	$131.88	$131.90	$131.90
Purchase #7	$103.54	6.554%	$110.326	$110.33	$110.35	$110.30
7 purchase totals =	$861.46		$932.3381	$932.34	$932.40	$932.40