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	$237.92	8.583%	$258.3407	$258.34	$258.35	$258.30
Purchase #2	$73.87	8.314%	$80.0116	$80.01	$80.00	$80.00
Purchase #3	$30.90	8.325%	$33.4724	$33.47	$33.45	$33.50
Purchase #4	$106.81	3.204%	$110.2322	$110.23	$110.25	$110.20
Purchase #5	$239.87	6.457%	$255.3584	$255.36	$255.35	$255.40
Purchase #6	$141.94	5.426%	$149.6417	$149.64	$149.65	$149.60
Purchase #7	$115.41	10.779%	$127.85	$127.85	$127.85	$127.90
7 purchase totals =	$946.72		$1,014.9070	$1,014.90	$1,014.90	$1,014.90