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	$34.65	5.374%	$36.5121	$36.51	$36.50	$36.50
Purchase #2	$85.26	6.408%	$90.7235	$90.72	$90.70	$90.70
Purchase #3	$101.33	3.546%	$104.9232	$104.92	$104.90	$104.90
Purchase #4	$212.37	12.296%	$238.483	$238.48	$238.50	$238.50
Purchase #5	$13.59	6.765%	$14.5094	$14.51	$14.50	$14.50
Purchase #6	$239.26	7.736%	$257.7692	$257.77	$257.75	$257.80
Purchase #7	$229.39	10.648%	$253.8154	$253.82	$253.80	$253.80
7 purchase totals =	$915.85		$996.7358	$996.73	$996.65	$996.70