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	$246.86	11.417%	$275.044	$275.04	$275.05	$275.00
Purchase #2	$199.45	3.354%	$206.1396	$206.14	$206.15	$206.10
Purchase #3	$15.42	7.105%	$16.5156	$16.52	$16.50	$16.50
Purchase #4	$151.57	12.859%	$171.0604	$171.06	$171.05	$171.10
Purchase #5	$86.60	11.339%	$96.4196	$96.42	$96.40	$96.40
Purchase #6	$177.83	3.493%	$184.0416	$184.04	$184.05	$184.00
Purchase #7	$146.73	6.461%	$156.2102	$156.21	$156.20	$156.20
7 purchase totals =	$1,024.46		$1,105.4310	$1,105.43	$1,105.40	$1,105.30