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	$18.60	3.410%	$19.2343	$19.23	$19.25	$19.20
Purchase #2	$74.38	8.311%	$80.5617	$80.56	$80.55	$80.60
Purchase #3	$149.64	11.161%	$166.3413	$166.34	$166.35	$166.30
Purchase #4	$156.44	9.334%	$171.0421	$171.04	$171.05	$171.00
Purchase #5	$173.36	13.285%	$196.3909	$196.39	$196.40	$196.40
Purchase #6	$200.44	12.688%	$225.8718	$225.87	$225.85	$225.90
Purchase #7	$160.70	11.814%	$179.6851	$179.69	$179.70	$179.70
7 purchase totals =	$933.56		$1,039.1272	$1,039.12	$1,039.15	$1,039.10