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	$83.81	11.805%	$93.7038	$93.70	$93.70	$93.70
Purchase #2	$114.29	10.610%	$126.4162	$126.42	$126.40	$126.40
Purchase #3	$193.43	6.623%	$206.2409	$206.24	$206.25	$206.20
Purchase #4	$74.59	11.689%	$83.3088	$83.31	$83.30	$83.30
Purchase #5	$195.62	13.289%	$221.6159	$221.62	$221.60	$221.60
Purchase #6	$89.32	12.466%	$100.4546	$100.45	$100.45	$100.50
Purchase #7	$172.67	13.870%	$196.6193	$196.62	$196.60	$196.60
7 purchase totals =	$923.73		$1,028.3595	$1,028.36	$1,028.30	$1,028.30