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	$119.67	10.226%	$131.9075	$131.91	$131.90	$131.90
Purchase #2	$133.71	12.258%	$150.1002	$150.10	$150.10	$150.10
Purchase #3	$123.60	12.113%	$138.5717	$138.57	$138.55	$138.60
Purchase #4	$153.26	10.445%	$169.268	$169.27	$169.25	$169.30
Purchase #5	$147.60	5.575%	$155.8287	$155.83	$155.85	$155.80
Purchase #6	$17.26	13.110%	$19.5228	$19.52	$19.50	$19.50
Purchase #7	$153.29	11.727%	$171.2663	$171.27	$171.25	$171.30
7 purchase totals =	$848.39		$936.4652	$936.47	$936.40	$936.50