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	$69.29	4.296%	$72.2667	$72.27	$72.25	$72.30
Purchase #2	$145.64	7.411%	$156.4334	$156.43	$156.45	$156.40
Purchase #3	$116.32	3.655%	$120.5715	$120.57	$120.55	$120.60
Purchase #4	$173.36	4.656%	$181.4316	$181.43	$181.45	$181.40
Purchase #5	$216.57	3.160%	$223.4136	$223.41	$223.40	$223.40
Purchase #6	$60.94	9.196%	$66.544	$66.54	$66.55	$66.50
Purchase #7	$27.78	7.303%	$29.8088	$29.81	$29.80	$29.80
7 purchase totals =	$809.90		$850.4696	$850.46	$850.45	$850.40