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	$42.28	8.590%	$45.9119	$45.91	$45.90	$45.90
Purchase #2	$13.81	8.291%	$14.955	$14.96	$14.95	$15.00
Purchase #3	$167.38	11.583%	$186.7676	$186.77	$186.75	$186.80
Purchase #4	$30.41	10.134%	$33.4917	$33.49	$33.50	$33.50
Purchase #5	$167.63	11.813%	$187.4321	$187.43	$187.45	$187.40
Purchase #6	$156.33	9.872%	$171.7629	$171.76	$171.75	$171.80
Purchase #7	$67.48	7.319%	$72.4189	$72.42	$72.40	$72.40
7 purchase totals =	$645.32		$712.7401	$712.74	$712.70	$712.80