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	$139.63	12.411%	$156.9595	$156.96	$156.95	$157.00
Purchase #2	$245.75	7.537%	$264.2722	$264.27	$264.25	$264.30
Purchase #3	$35.62	4.651%	$37.2767	$37.28	$37.30	$37.30
Purchase #4	$227.86	12.251%	$255.7751	$255.78	$255.80	$255.80
Purchase #5	$151.41	4.376%	$158.0357	$158.04	$158.05	$158.00
Purchase #6	$238.43	11.585%	$266.0521	$266.05	$266.05	$266.10
Purchase #7	$232.76	12.226%	$261.2172	$261.22	$261.20	$261.20
7 purchase totals =	$1,271.46		$1,399.5885	$1,399.60	$1,399.60	$1,399.70