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	$166.32	4.817%	$174.3316	$174.33	$174.35	$174.30
Purchase #2	$237.98	11.178%	$264.5814	$264.58	$264.60	$264.60
Purchase #3	$184.81	13.257%	$209.3103	$209.31	$209.30	$209.30
Purchase #4	$243.56	10.575%	$269.3165	$269.32	$269.30	$269.30
Purchase #5	$94.29	9.765%	$103.4974	$103.50	$103.50	$103.50
Purchase #6	$14.54	5.198%	$15.2958	$15.30	$15.30	$15.30
Purchase #7	$34.85	11.673%	$38.918	$38.92	$38.90	$38.90
7 purchase totals =	$976.35		$1,075.2510	$1,075.26	$1,075.25	$1,075.20