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	$123.38	6.789%	$131.7563	$131.76	$131.75	$131.80
Purchase #2	$187.55	4.693%	$196.3517	$196.35	$196.35	$196.40
Purchase #3	$159.31	9.747%	$174.8379	$174.84	$174.85	$174.80
Purchase #4	$8.70	3.116%	$8.9711	$8.97	$8.95	$9.00
Purchase #5	$45.56	10.605%	$50.3916	$50.39	$50.40	$50.40
Purchase #6	$223.61	8.408%	$242.4111	$242.41	$242.40	$242.40
Purchase #7	$140.51	5.536%	$148.2886	$148.29	$148.30	$148.30
7 purchase totals =	$888.62		$953.0083	$953.01	$953.00	$953.10