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	$112.89	13.440%	$128.0624	$128.06	$128.05	$128.10
Purchase #2	$100.60	4.483%	$105.1099	$105.11	$105.10	$105.10
Purchase #3	$200.54	11.371%	$223.3434	$223.34	$223.35	$223.30
Purchase #4	$169.67	3.730%	$175.9987	$176.00	$176.00	$176.00
Purchase #5	$91.76	10.147%	$101.0709	$101.07	$101.05	$101.10
Purchase #6	$238.76	8.104%	$258.1091	$258.11	$258.10	$258.10
Purchase #7	$147.71	10.193%	$162.7661	$162.77	$162.75	$162.80
7 purchase totals =	$1,061.93		$1,154.4605	$1,154.46	$1,154.40	$1,154.50