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	$114.48	4.146%	$119.2263	$119.23	$119.25	$119.20
Purchase #2	$78.56	4.816%	$82.3434	$82.34	$82.35	$82.30
Purchase #3	$12.33	3.335%	$12.7412	$12.74	$12.75	$12.70
Purchase #4	$62.37	9.394%	$68.229	$68.23	$68.25	$68.20
Purchase #5	$221.74	9.524%	$242.8585	$242.86	$242.85	$242.90
Purchase #6	$250.94	3.615%	$260.0115	$260.01	$260.00	$260.00
Purchase #7	$32.52	4.373%	$33.9421	$33.94	$33.95	$33.90
7 purchase totals =	$772.94		$819.3520	$819.35	$819.40	$819.20