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	$182.81	6.303%	$194.3325	$194.33	$194.35	$194.30
Purchase #2	$233.45	11.564%	$260.4462	$260.45	$260.45	$260.40
Purchase #3	$41.86	9.740%	$45.9372	$45.94	$45.95	$45.90
Purchase #4	$66.88	5.522%	$70.5731	$70.57	$70.55	$70.60
Purchase #5	$20.95	4.454%	$21.8831	$21.88	$21.90	$21.90
Purchase #6	$139.87	6.453%	$148.8958	$148.90	$148.90	$148.90
Purchase #7	$192.85	13.329%	$218.555	$218.56	$218.55	$218.60
7 purchase totals =	$878.67		$960.6229	$960.63	$960.65	$960.60