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	$123.78	3.120%	$127.6419	$127.64	$127.65	$127.60
Purchase #2	$203.49	4.826%	$213.3104	$213.31	$213.30	$213.30
Purchase #3	$149.55	12.746%	$168.6116	$168.61	$168.60	$168.60
Purchase #4	$133.57	6.598%	$142.3829	$142.38	$142.40	$142.40
Purchase #5	$93.50	6.305%	$99.3952	$99.40	$99.40	$99.40
Purchase #6	$185.28	7.310%	$198.824	$198.82	$198.80	$198.80
Purchase #7	$61.28	6.120%	$65.0303	$65.03	$65.05	$65.00
7 purchase totals =	$950.45		$1,015.1963	$1,015.19	$1,015.20	$1,015.10