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	$76.28	9.125%	$83.2406	$83.24	$83.25	$83.20
Purchase #2	$196.37	5.657%	$207.4787	$207.48	$207.50	$207.50
Purchase #3	$244.79	5.741%	$258.8434	$258.84	$258.85	$258.80
Purchase #4	$78.73	6.488%	$83.838	$83.84	$83.85	$83.80
Purchase #5	$221.62	7.591%	$238.4432	$238.44	$238.45	$238.40
Purchase #6	$76.81	7.349%	$82.4548	$82.45	$82.45	$82.50
Purchase #7	$105.83	3.601%	$109.6409	$109.64	$109.65	$109.60
7 purchase totals =	$1,000.43		$1,063.9396	$1,063.93	$1,064.00	$1,063.80