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	$144.45	3.814%	$149.9593	$149.96	$149.95	$150.00
Purchase #2	$33.40	6.543%	$35.5854	$35.59	$35.60	$35.60
Purchase #3	$151.91	8.564%	$164.9196	$164.92	$164.90	$164.90
Purchase #4	$101.60	7.352%	$109.0696	$109.07	$109.05	$109.10
Purchase #5	$233.85	3.418%	$241.843	$241.84	$241.85	$241.80
Purchase #6	$53.72	11.849%	$60.0853	$60.09	$60.10	$60.10
Purchase #7	$213.80	12.256%	$240.0033	$240.00	$240.00	$240.00
7 purchase totals =	$932.73		$1,001.4655	$1,001.47	$1,001.45	$1,001.50