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	$223.25	13.418%	$253.2057	$253.21	$253.20	$253.20
Purchase #2	$241.49	9.782%	$265.1126	$265.11	$265.10	$265.10
Purchase #3	$186.74	5.180%	$196.4131	$196.41	$196.40	$196.40
Purchase #4	$142.38	9.187%	$155.4605	$155.46	$155.45	$155.50
Purchase #5	$222.38	4.863%	$233.1943	$233.19	$233.20	$233.20
Purchase #6	$140.96	4.350%	$147.0918	$147.09	$147.10	$147.10
Purchase #7	$46.63	10.382%	$51.4711	$51.47	$51.45	$51.50
7 purchase totals =	$1,203.83		$1,301.9491	$1,301.94	$1,301.90	$1,302.00