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	$174.58	9.596%	$191.3327	$191.33	$191.35	$191.30
Purchase #2	$246.66	3.709%	$255.8086	$255.81	$255.80	$255.80
Purchase #3	$91.34	11.198%	$101.5683	$101.57	$101.55	$101.60
Purchase #4	$169.40	13.717%	$192.6366	$192.64	$192.65	$192.60
Purchase #5	$138.34	5.111%	$145.4106	$145.41	$145.40	$145.40
Purchase #6	$151.47	13.526%	$171.9578	$171.96	$171.95	$172.00
Purchase #7	$43.58	6.239%	$46.299	$46.30	$46.30	$46.30
7 purchase totals =	$1,015.37		$1,105.0136	$1,105.02	$1,105.00	$1,105.00