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	$99.61	6.272%	$105.8575	$105.86	$105.85	$105.90
Purchase #2	$139.36	6.719%	$148.7236	$148.72	$148.70	$148.70
Purchase #3	$196.56	13.648%	$223.3865	$223.39	$223.40	$223.40
Purchase #4	$126.26	8.265%	$136.6954	$136.70	$136.70	$136.70
Purchase #5	$170.79	3.161%	$176.1887	$176.19	$176.20	$176.20
Purchase #6	$82.37	9.617%	$90.2915	$90.29	$90.30	$90.30
Purchase #7	$158.66	8.185%	$171.6463	$171.65	$171.65	$171.60
7 purchase totals =	$973.61		$1,052.7895	$1,052.80	$1,052.80	$1,052.80