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	$229.46	9.568%	$251.4147	$251.41	$251.40	$251.40
Purchase #2	$126.78	3.731%	$131.5102	$131.51	$131.50	$131.50
Purchase #3	$31.35	13.254%	$35.5051	$35.51	$35.50	$35.50
Purchase #4	$53.58	10.651%	$59.2868	$59.29	$59.30	$59.30
Purchase #5	$153.94	8.635%	$167.2327	$167.23	$167.25	$167.20
Purchase #6	$34.34	9.568%	$37.6257	$37.63	$37.65	$37.60
Purchase #7	$223.33	5.656%	$235.9615	$235.96	$235.95	$236.00
7 purchase totals =	$852.78		$918.5367	$918.54	$918.55	$918.50