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	$113.78	3.759%	$118.057	$118.06	$118.05	$118.10
Purchase #2	$199.89	10.694%	$221.2662	$221.27	$221.25	$221.30
Purchase #3	$38.93	9.729%	$42.7175	$42.72	$42.70	$42.70
Purchase #4	$19.27	10.440%	$21.2818	$21.28	$21.30	$21.30
Purchase #5	$85.57	7.744%	$92.1965	$92.20	$92.20	$92.20
Purchase #6	$112.95	5.485%	$119.1453	$119.15	$119.15	$119.10
Purchase #7	$147.91	5.722%	$156.3734	$156.37	$156.35	$156.40
7 purchase totals =	$718.30		$771.0377	$771.05	$771.00	$771.10