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	$186.62	13.653%	$212.0992	$212.10	$212.10	$212.10
Purchase #2	$177.72	3.845%	$184.5533	$184.55	$184.55	$184.60
Purchase #3	$12.68	5.169%	$13.3354	$13.34	$13.35	$13.30
Purchase #4	$139.59	5.752%	$147.6192	$147.62	$147.60	$147.60
Purchase #5	$32.42	3.512%	$33.5586	$33.56	$33.55	$33.60
Purchase #6	$153.92	11.314%	$171.3345	$171.33	$171.35	$171.30
Purchase #7	$37.37	5.502%	$39.4261	$39.43	$39.45	$39.40
7 purchase totals =	$740.32		$801.9263	$801.93	$801.95	$801.90