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	$84.69	7.656%	$91.1739	$91.17	$91.15	$91.20
Purchase #2	$152.29	13.700%	$173.1537	$173.15	$173.15	$173.20
Purchase #3	$152.46	9.207%	$166.497	$166.50	$166.50	$166.50
Purchase #4	$47.51	12.337%	$53.3713	$53.37	$53.35	$53.40
Purchase #5	$85.55	11.675%	$95.538	$95.54	$95.55	$95.50
Purchase #6	$134.88	3.670%	$139.8301	$139.83	$139.85	$139.80
Purchase #7	$43.58	12.443%	$49.0027	$49.00	$49.00	$49.00
7 purchase totals =	$700.96		$768.5667	$768.56	$768.55	$768.60