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	$133.58	12.568%	$150.3683	$150.37	$150.35	$150.40
Purchase #2	$198.36	5.333%	$208.9385	$208.94	$208.95	$208.90
Purchase #3	$116.65	11.261%	$129.786	$129.79	$129.80	$129.80
Purchase #4	$141.53	12.287%	$158.9198	$158.92	$158.90	$158.90
Purchase #5	$153.64	9.126%	$167.6612	$167.66	$167.65	$167.70
Purchase #6	$186.33	5.292%	$196.1906	$196.19	$196.20	$196.20
Purchase #7	$80.74	13.379%	$91.5422	$91.54	$91.55	$91.50
7 purchase totals =	$1,010.83		$1,103.4066	$1,103.41	$1,103.40	$1,103.40