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	$191.98	13.156%	$217.2369	$217.24	$217.25	$217.20
Purchase #2	$247.86	7.451%	$266.328	$266.33	$266.35	$266.30
Purchase #3	$102.61	13.534%	$116.4972	$116.50	$116.50	$116.50
Purchase #4	$140.44	8.412%	$152.2538	$152.25	$152.25	$152.30
Purchase #5	$53.41	12.213%	$59.933	$59.93	$59.95	$59.90
Purchase #6	$217.44	9.495%	$238.0859	$238.09	$238.10	$238.10
Purchase #7	$210.43	8.405%	$228.1166	$228.12	$228.10	$228.10
7 purchase totals =	$1,164.17		$1,278.4514	$1,278.46	$1,278.50	$1,278.40