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	$147.82	3.763%	$153.3825	$153.38	$153.40	$153.40
Purchase #2	$35.25	10.806%	$39.0591	$39.06	$39.05	$39.10
Purchase #3	$187.94	11.865%	$210.2391	$210.24	$210.25	$210.20
Purchase #4	$146.92	11.664%	$164.0567	$164.06	$164.05	$164.10
Purchase #5	$68.31	4.829%	$71.6087	$71.61	$71.60	$71.60
Purchase #6	$19.78	3.644%	$20.5008	$20.50	$20.50	$20.50
Purchase #7	$108.70	4.397%	$113.4795	$113.48	$113.50	$113.50
7 purchase totals =	$714.72		$772.3264	$772.33	$772.35	$772.40