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	$215.43	3.129%	$222.1708	$222.17	$222.15	$222.20
Purchase #2	$227.34	3.519%	$235.3401	$235.34	$235.35	$235.30
Purchase #3	$18.67	6.492%	$19.8821	$19.88	$19.90	$19.90
Purchase #4	$174.44	6.502%	$185.7821	$185.78	$185.80	$185.80
Purchase #5	$28.75	11.766%	$32.1327	$32.13	$32.15	$32.10
Purchase #6	$155.68	5.418%	$164.1147	$164.11	$164.10	$164.10
Purchase #7	$112.78	9.727%	$123.7501	$123.75	$123.75	$123.80
7 purchase totals =	$933.09		$983.1726	$983.16	$983.20	$983.20