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	$233.46	12.763%	$263.2565	$263.26	$263.25	$263.30
Purchase #2	$220.64	4.738%	$231.0939	$231.09	$231.10	$231.10
Purchase #3	$24.97	10.417%	$27.5711	$27.57	$27.55	$27.60
Purchase #4	$190.53	9.478%	$208.5884	$208.59	$208.60	$208.60
Purchase #5	$245.49	9.472%	$268.7428	$268.74	$268.75	$268.70
Purchase #6	$114.55	3.347%	$118.384	$118.38	$118.40	$118.40
Purchase #7	$171.31	11.429%	$190.889	$190.89	$190.90	$190.90
7 purchase totals =	$1,200.95		$1,308.5257	$1,308.52	$1,308.55	$1,308.60