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	$183.30	7.322%	$196.7212	$196.72	$196.70	$196.70
Purchase #2	$146.30	4.611%	$153.0459	$153.05	$153.05	$153.00
Purchase #3	$12.46	8.200%	$13.4817	$13.48	$13.50	$13.50
Purchase #4	$89.47	13.339%	$101.4044	$101.40	$101.40	$101.40
Purchase #5	$77.72	3.519%	$80.455	$80.46	$80.45	$80.50
Purchase #6	$202.44	10.334%	$223.3601	$223.36	$223.35	$223.40
Purchase #7	$69.58	12.419%	$78.2211	$78.22	$78.20	$78.20
7 purchase totals =	$781.27		$846.6894	$846.69	$846.65	$846.70