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	$150.72	3.565%	$156.0932	$156.09	$156.10	$156.10
Purchase #2	$116.91	4.867%	$122.6	$122.60	$122.60	$122.60
Purchase #3	$188.38	4.400%	$196.6687	$196.67	$196.65	$196.70
Purchase #4	$56.55	7.605%	$60.8506	$60.85	$60.85	$60.90
Purchase #5	$96.49	6.139%	$102.4135	$102.41	$102.40	$102.40
Purchase #6	$43.38	9.377%	$47.4477	$47.45	$47.45	$47.40
Purchase #7	$70.38	13.638%	$79.9784	$79.98	$80.00	$80.00
7 purchase totals =	$722.81		$766.0521	$766.05	$766.05	$766.10