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	$196.76	6.444%	$209.4392	$209.44	$209.45	$209.40
Purchase #2	$45.78	11.493%	$51.0415	$51.04	$51.05	$51.00
Purchase #3	$140.83	10.864%	$156.1298	$156.13	$156.15	$156.10
Purchase #4	$201.56	4.418%	$210.4649	$210.46	$210.45	$210.50
Purchase #5	$121.47	7.414%	$130.4758	$130.48	$130.50	$130.50
Purchase #6	$155.60	5.776%	$164.5875	$164.59	$164.60	$164.60
Purchase #7	$94.29	7.541%	$101.4004	$101.40	$101.40	$101.40
7 purchase totals =	$956.29		$1,023.5391	$1,023.54	$1,023.60	$1,023.50