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	$101.99	7.817%	$109.9626	$109.96	$109.95	$110.00
Purchase #2	$122.41	8.119%	$132.3485	$132.35	$132.35	$132.30
Purchase #3	$231.72	11.842%	$259.1603	$259.16	$259.15	$259.20
Purchase #4	$99.37	3.656%	$103.003	$103.00	$103.00	$103.00
Purchase #5	$148.88	9.387%	$162.8554	$162.86	$162.85	$162.90
Purchase #6	$151.50	9.832%	$166.3955	$166.40	$166.40	$166.40
Purchase #7	$63.76	8.457%	$69.1522	$69.15	$69.15	$69.20
7 purchase totals =	$919.63		$1,002.8775	$1,002.88	$1,002.85	$1,003.00