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	$92.31	12.583%	$103.9254	$103.93	$103.95	$103.90
Purchase #2	$144.46	13.776%	$164.3608	$164.36	$164.35	$164.40
Purchase #3	$198.75	10.162%	$218.947	$218.95	$218.95	$218.90
Purchase #4	$215.44	9.494%	$235.8939	$235.89	$235.90	$235.90
Purchase #5	$73.95	12.185%	$82.9608	$82.96	$82.95	$83.00
Purchase #6	$185.77	3.376%	$192.0416	$192.04	$192.05	$192.00
Purchase #7	$60.55	10.846%	$67.1173	$67.12	$67.10	$67.10
7 purchase totals =	$971.23		$1,065.2468	$1,065.25	$1,065.25	$1,065.20