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	$144.57	5.400%	$152.3768	$152.38	$152.40	$152.40
Purchase #2	$106.81	4.674%	$111.8023	$111.80	$111.80	$111.80
Purchase #3	$56.55	6.103%	$60.0012	$60.00	$60.00	$60.00
Purchase #4	$14.89	7.818%	$16.0541	$16.05	$16.05	$16.10
Purchase #5	$171.91	5.838%	$181.9461	$181.95	$181.95	$181.90
Purchase #6	$77.64	4.213%	$80.911	$80.91	$80.90	$80.90
Purchase #7	$90.69	13.341%	$102.789	$102.79	$102.80	$102.80
7 purchase totals =	$663.06		$705.8805	$705.88	$705.90	$705.90