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	$104.48	4.816%	$109.5118	$109.51	$109.50	$109.50
Purchase #2	$38.52	12.326%	$43.268	$43.27	$43.25	$43.30
Purchase #3	$203.37	10.871%	$225.4784	$225.48	$225.50	$225.50
Purchase #4	$239.59	4.868%	$251.2532	$251.25	$251.25	$251.30
Purchase #5	$54.72	7.582%	$58.8689	$58.87	$58.85	$58.90
Purchase #6	$214.85	8.811%	$233.7804	$233.78	$233.80	$233.80
Purchase #7	$149.74	10.194%	$165.0045	$165.00	$165.00	$165.00
7 purchase totals =	$1,005.27		$1,087.1652	$1,087.16	$1,087.15	$1,087.30