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	$76.98	7.738%	$82.9367	$82.94	$82.95	$82.90
Purchase #2	$54.26	12.305%	$60.9367	$60.94	$60.95	$60.90
Purchase #3	$208.94	10.730%	$231.3593	$231.36	$231.35	$231.40
Purchase #4	$7.97	11.645%	$8.8981	$8.90	$8.90	$8.90
Purchase #5	$34.33	5.846%	$36.3369	$36.34	$36.35	$36.30
Purchase #6	$79.89	11.555%	$89.1213	$89.12	$89.10	$89.10
Purchase #7	$250.48	5.176%	$263.4448	$263.44	$263.45	$263.40
7 purchase totals =	$712.85		$773.0338	$773.04	$773.05	$772.90