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	$233.25	7.151%	$249.9297	$249.93	$249.95	$249.90
Purchase #2	$15.83	8.308%	$17.1452	$17.15	$17.15	$17.10
Purchase #3	$142.54	6.655%	$152.026	$152.03	$152.05	$152.00
Purchase #4	$138.46	10.273%	$152.684	$152.68	$152.70	$152.70
Purchase #5	$145.91	13.757%	$165.9828	$165.98	$166.00	$166.00
Purchase #6	$92.40	13.804%	$105.1549	$105.15	$105.15	$105.20
Purchase #7	$200.72	9.229%	$219.2444	$219.24	$219.25	$219.20
7 purchase totals =	$969.11		$1,062.1670	$1,062.16	$1,062.25	$1,062.10