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	$181.94	9.605%	$199.4153	$199.42	$199.40	$199.40
Purchase #2	$51.34	4.194%	$53.4932	$53.49	$53.50	$53.50
Purchase #3	$186.52	7.316%	$200.1658	$200.17	$200.15	$200.20
Purchase #4	$6.38	11.711%	$7.1272	$7.13	$7.15	$7.10
Purchase #5	$200.52	5.258%	$211.0633	$211.06	$211.05	$211.10
Purchase #6	$144.93	5.318%	$152.6374	$152.64	$152.65	$152.60
Purchase #7	$208.57	4.355%	$217.6532	$217.65	$217.65	$217.70
7 purchase totals =	$980.20		$1,041.5554	$1,041.56	$1,041.55	$1,041.60