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	$153.83	13.518%	$174.6247	$174.62	$174.60	$174.60
Purchase #2	$112.27	12.583%	$126.3969	$126.40	$126.40	$126.40
Purchase #3	$54.72	6.572%	$58.3162	$58.32	$58.30	$58.30
Purchase #4	$200.85	11.330%	$223.6063	$223.61	$223.60	$223.60
Purchase #5	$130.49	6.545%	$139.0306	$139.03	$139.05	$139.00
Purchase #6	$20.66	6.766%	$22.0579	$22.06	$22.05	$22.10
Purchase #7	$177.65	5.429%	$187.2946	$187.29	$187.30	$187.30
7 purchase totals =	$850.47		$931.3272	$931.33	$931.30	$931.30