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	$138.50	8.794%	$150.6797	$150.68	$150.70	$150.70
Purchase #2	$79.41	4.381%	$82.889	$82.89	$82.90	$82.90
Purchase #3	$79.37	3.847%	$82.4234	$82.42	$82.40	$82.40
Purchase #4	$119.62	12.793%	$134.923	$134.92	$134.90	$134.90
Purchase #5	$246.37	7.591%	$265.0719	$265.07	$265.05	$265.10
Purchase #6	$215.63	12.671%	$242.9525	$242.95	$242.95	$243.00
Purchase #7	$212.46	11.728%	$237.3773	$237.38	$237.40	$237.40
7 purchase totals =	$1,091.36		$1,196.3168	$1,196.31	$1,196.30	$1,196.40