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	$45.57	4.291%	$47.5254	$47.53	$47.55	$47.50
Purchase #2	$74.49	9.555%	$81.6075	$81.61	$81.60	$81.60
Purchase #3	$55.92	6.607%	$59.6146	$59.61	$59.60	$59.60
Purchase #4	$236.51	5.660%	$249.8965	$249.90	$249.90	$249.90
Purchase #5	$201.55	6.341%	$214.3303	$214.33	$214.35	$214.30
Purchase #6	$166.30	7.532%	$178.8257	$178.83	$178.85	$178.80
Purchase #7	$141.38	7.501%	$151.9849	$151.98	$152.00	$152.00
7 purchase totals =	$921.72		$983.7849	$983.79	$983.85	$983.70