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	$131.87	6.752%	$140.7739	$140.77	$140.75	$140.80
Purchase #2	$75.98	13.532%	$86.2616	$86.26	$86.25	$86.30
Purchase #3	$52.91	5.712%	$55.9322	$55.93	$55.95	$55.90
Purchase #4	$78.92	3.119%	$81.3815	$81.38	$81.40	$81.40
Purchase #5	$50.74	12.560%	$57.1129	$57.11	$57.10	$57.10
Purchase #6	$85.85	8.254%	$92.9361	$92.94	$92.95	$92.90
Purchase #7	$189.82	3.504%	$196.4713	$196.47	$196.45	$196.50
7 purchase totals =	$666.09		$710.8695	$710.86	$710.85	$710.90