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	$136.79	10.322%	$150.9095	$150.91	$150.90	$150.90
Purchase #2	$105.97	3.206%	$109.3674	$109.37	$109.35	$109.40
Purchase #3	$87.59	11.614%	$97.7627	$97.76	$97.75	$97.80
Purchase #4	$165.65	8.204%	$179.2399	$179.24	$179.25	$179.20
Purchase #5	$6.80	5.246%	$7.1567	$7.16	$7.15	$7.20
Purchase #6	$196.30	12.862%	$221.5481	$221.55	$221.55	$221.50
Purchase #7	$182.41	7.621%	$196.3115	$196.31	$196.30	$196.30
7 purchase totals =	$881.51		$962.2958	$962.30	$962.25	$962.30