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	$33.90	13.261%	$38.3955	$38.40	$38.40	$38.40
Purchase #2	$18.62	5.369%	$19.6197	$19.62	$19.60	$19.60
Purchase #3	$168.89	7.592%	$181.7121	$181.71	$181.70	$181.70
Purchase #4	$238.30	11.497%	$265.6974	$265.70	$265.70	$265.70
Purchase #5	$209.47	4.704%	$219.3235	$219.32	$219.30	$219.30
Purchase #6	$160.89	12.423%	$180.8774	$180.88	$180.90	$180.90
Purchase #7	$135.31	4.518%	$141.4233	$141.42	$141.40	$141.40
7 purchase totals =	$965.38		$1,047.0489	$1,047.05	$1,047.00	$1,047.00