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	$228.52	9.815%	$250.9492	$250.95	$250.95	$250.90
Purchase #2	$54.47	9.401%	$59.5907	$59.59	$59.60	$59.60
Purchase #3	$34.36	7.808%	$37.0428	$37.04	$37.05	$37.00
Purchase #4	$231.74	5.711%	$244.9747	$244.97	$244.95	$245.00
Purchase #5	$98.96	13.587%	$112.4057	$112.41	$112.40	$112.40
Purchase #6	$210.97	4.693%	$220.8708	$220.87	$220.85	$220.90
Purchase #7	$86.91	3.500%	$89.9519	$89.95	$89.95	$90.00
7 purchase totals =	$945.93		$1,015.7858	$1,015.78	$1,015.75	$1,015.80