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	$151.53	10.264%	$167.083	$167.08	$167.10	$167.10
Purchase #2	$178.41	10.301%	$196.788	$196.79	$196.80	$196.80
Purchase #3	$34.32	6.119%	$36.42	$36.42	$36.40	$36.40
Purchase #4	$243.95	12.228%	$273.7802	$273.78	$273.80	$273.80
Purchase #5	$47.43	12.292%	$53.2601	$53.26	$53.25	$53.30
Purchase #6	$185.92	12.173%	$208.552	$208.55	$208.55	$208.60
Purchase #7	$164.90	13.692%	$187.4781	$187.48	$187.50	$187.50
7 purchase totals =	$1,006.46		$1,123.3614	$1,123.36	$1,123.40	$1,123.50