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	$166.72	4.269%	$173.8373	$173.84	$173.85	$173.80
Purchase #2	$157.27	4.307%	$164.0436	$164.04	$164.05	$164.00
Purchase #3	$207.48	8.651%	$225.4291	$225.43	$225.45	$225.40
Purchase #4	$50.44	7.264%	$54.104	$54.10	$54.10	$54.10
Purchase #5	$94.72	5.724%	$100.1418	$100.14	$100.15	$100.10
Purchase #6	$201.95	4.392%	$210.8196	$210.82	$210.80	$210.80
Purchase #7	$174.69	8.109%	$188.8556	$188.86	$188.85	$188.90
7 purchase totals =	$1,053.27		$1,117.2310	$1,117.23	$1,117.25	$1,117.10