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	$175.71	12.830%	$198.2536	$198.25	$198.25	$198.30
Purchase #2	$234.71	13.134%	$265.5368	$265.54	$265.55	$265.50
Purchase #3	$137.29	6.270%	$145.8981	$145.90	$145.90	$145.90
Purchase #4	$13.44	13.374%	$15.2375	$15.24	$15.25	$15.20
Purchase #5	$218.59	9.816%	$240.0468	$240.05	$240.05	$240.00
Purchase #6	$90.53	8.826%	$98.5202	$98.52	$98.50	$98.50
Purchase #7	$43.50	9.110%	$47.4629	$47.46	$47.45	$47.50
7 purchase totals =	$913.77		$1,010.9559	$1,010.96	$1,010.95	$1,010.90