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	$180.29	10.398%	$199.0366	$199.04	$199.05	$199.00
Purchase #2	$114.45	11.446%	$127.5499	$127.55	$127.55	$127.50
Purchase #3	$130.60	7.660%	$140.604	$140.60	$140.60	$140.60
Purchase #4	$99.59	3.832%	$103.4063	$103.41	$103.40	$103.40
Purchase #5	$242.45	5.500%	$255.7848	$255.78	$255.80	$255.80
Purchase #6	$51.93	10.228%	$57.2414	$57.24	$57.25	$57.20
Purchase #7	$167.93	3.814%	$174.3349	$174.33	$174.35	$174.30
7 purchase totals =	$987.24		$1,057.9579	$1,057.95	$1,058.00	$1,057.80