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	$156.98	5.567%	$165.7191	$165.72	$165.70	$165.70
Purchase #2	$83.86	11.165%	$93.223	$93.22	$93.20	$93.20
Purchase #3	$98.80	9.256%	$107.9449	$107.94	$107.95	$107.90
Purchase #4	$83.80	7.715%	$90.2652	$90.27	$90.25	$90.30
Purchase #5	$152.53	10.152%	$168.0148	$168.01	$168.00	$168.00
Purchase #6	$103.38	13.282%	$117.1109	$117.11	$117.10	$117.10
Purchase #7	$204.29	13.342%	$231.5464	$231.55	$231.55	$231.50
7 purchase totals =	$883.64		$973.8243	$973.82	$973.75	$973.70