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	$151.37	13.289%	$171.4856	$171.49	$171.50	$171.50
Purchase #2	$130.87	4.768%	$137.1099	$137.11	$137.10	$137.10
Purchase #3	$167.71	5.474%	$176.8904	$176.89	$176.90	$176.90
Purchase #4	$133.82	12.764%	$150.9008	$150.90	$150.90	$150.90
Purchase #5	$164.66	10.274%	$181.5772	$181.58	$181.60	$181.60
Purchase #6	$169.44	12.309%	$190.2964	$190.30	$190.30	$190.30
Purchase #7	$189.44	5.453%	$199.7702	$199.77	$199.75	$199.80
7 purchase totals =	$1,107.31		$1,208.0305	$1,208.04	$1,208.05	$1,208.10