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	$99.91	3.700%	$103.6067	$103.61	$103.60	$103.60
Purchase #2	$30.31	4.739%	$31.7464	$31.75	$31.75	$31.70
Purchase #3	$242.32	6.199%	$257.3414	$257.34	$257.35	$257.30
Purchase #4	$45.34	9.630%	$49.7062	$49.71	$49.70	$49.70
Purchase #5	$90.95	5.831%	$96.2533	$96.25	$96.25	$96.30
Purchase #6	$196.35	6.635%	$209.3778	$209.38	$209.40	$209.40
Purchase #7	$119.81	3.191%	$123.6331	$123.63	$123.65	$123.60
7 purchase totals =	$824.99		$871.6649	$871.67	$871.70	$871.60