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	$222.47	5.160%	$233.9495	$233.95	$233.95	$233.90
Purchase #2	$94.58	12.666%	$106.5595	$106.56	$106.55	$106.60
Purchase #3	$101.85	3.587%	$105.5034	$105.50	$105.50	$105.50
Purchase #4	$61.67	3.138%	$63.6052	$63.61	$63.60	$63.60
Purchase #5	$160.25	10.218%	$176.6243	$176.62	$176.60	$176.60
Purchase #6	$168.95	11.224%	$187.9129	$187.91	$187.90	$187.90
Purchase #7	$132.88	10.221%	$146.4617	$146.46	$146.45	$146.50
7 purchase totals =	$942.65		$1,020.6165	$1,020.61	$1,020.55	$1,020.60