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	$98.48	5.413%	$103.8107	$103.81	$103.80	$103.80
Purchase #2	$13.59	4.258%	$14.1687	$14.17	$14.15	$14.20
Purchase #3	$19.29	6.715%	$20.5853	$20.59	$20.60	$20.60
Purchase #4	$40.95	10.372%	$45.1973	$45.20	$45.20	$45.20
Purchase #5	$147.79	13.287%	$167.4269	$167.43	$167.45	$167.40
Purchase #6	$6.94	4.443%	$7.2483	$7.25	$7.25	$7.20
Purchase #7	$198.58	5.424%	$209.351	$209.35	$209.35	$209.40
7 purchase totals =	$525.62		$567.7882	$567.80	$567.80	$567.80