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	$208.78	6.435%	$222.215	$222.22	$222.20	$222.20
Purchase #2	$8.49	4.857%	$8.9024	$8.90	$8.90	$8.90
Purchase #3	$244.72	9.667%	$268.3771	$268.38	$268.40	$268.40
Purchase #4	$101.41	8.721%	$110.254	$110.25	$110.25	$110.30
Purchase #5	$118.93	10.508%	$131.4272	$131.43	$131.45	$131.40
Purchase #6	$230.58	8.609%	$250.4306	$250.43	$250.45	$250.40
Purchase #7	$141.94	10.453%	$156.777	$156.78	$156.80	$156.80
7 purchase totals =	$1,054.85		$1,148.3833	$1,148.39	$1,148.45	$1,148.40