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	$89.60	10.144%	$98.689	$98.69	$98.70	$98.70
Purchase #2	$54.41	3.253%	$56.18	$56.18	$56.20	$56.20
Purchase #3	$56.28	5.325%	$59.2769	$59.28	$59.30	$59.30
Purchase #4	$123.92	10.644%	$137.11	$137.11	$137.10	$137.10
Purchase #5	$11.38	7.414%	$12.2237	$12.22	$12.20	$12.20
Purchase #6	$141.70	4.527%	$148.1148	$148.11	$148.10	$148.10
Purchase #7	$95.71	3.868%	$99.4121	$99.41	$99.40	$99.40
7 purchase totals =	$573.00		$611.0065	$611.00	$611.00	$611.00