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	$184.60	6.605%	$196.7928	$196.79	$196.80	$196.80
Purchase #2	$205.73	5.219%	$216.467	$216.47	$216.45	$216.50
Purchase #3	$71.78	12.231%	$80.5594	$80.56	$80.55	$80.60
Purchase #4	$134.29	5.629%	$141.8492	$141.85	$141.85	$141.80
Purchase #5	$240.42	3.749%	$249.4333	$249.43	$249.45	$249.40
Purchase #6	$33.73	6.383%	$35.883	$35.88	$35.90	$35.90
Purchase #7	$237.33	5.357%	$250.0438	$250.04	$250.05	$250.00
7 purchase totals =	$1,107.88		$1,171.0285	$1,171.02	$1,171.05	$1,171.00