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	$89.54	3.465%	$92.6426	$92.64	$92.65	$92.60
Purchase #2	$43.29	11.794%	$48.3956	$48.40	$48.40	$48.40
Purchase #3	$61.53	9.425%	$67.3292	$67.33	$67.35	$67.30
Purchase #4	$241.51	7.388%	$259.3528	$259.35	$259.35	$259.40
Purchase #5	$57.80	12.282%	$64.899	$64.90	$64.90	$64.90
Purchase #6	$143.79	12.307%	$161.4862	$161.49	$161.50	$161.50
Purchase #7	$29.40	8.554%	$31.9149	$31.91	$31.90	$31.90
7 purchase totals =	$666.86		$726.0203	$726.02	$726.05	$726.00