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	$183.69	9.124%	$200.4499	$200.45	$200.45	$200.40
Purchase #2	$152.66	9.505%	$167.1703	$167.17	$167.15	$167.20
Purchase #3	$33.69	3.275%	$34.7933	$34.79	$34.80	$34.80
Purchase #4	$210.76	10.194%	$232.2449	$232.24	$232.25	$232.20
Purchase #5	$213.33	8.512%	$231.4886	$231.49	$231.50	$231.50
Purchase #6	$18.58	10.438%	$20.5194	$20.52	$20.50	$20.50
Purchase #7	$39.97	13.860%	$45.5098	$45.51	$45.50	$45.50
7 purchase totals =	$852.68		$932.1762	$932.17	$932.15	$932.10