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	$179.35	9.576%	$196.5246	$196.52	$196.50	$196.50
Purchase #2	$75.54	8.663%	$82.084	$82.08	$82.10	$82.10
Purchase #3	$201.63	8.359%	$218.4843	$218.48	$218.50	$218.50
Purchase #4	$234.59	5.758%	$248.0977	$248.10	$248.10	$248.10
Purchase #5	$195.81	8.206%	$211.8782	$211.88	$211.90	$211.90
Purchase #6	$62.59	13.870%	$71.2712	$71.27	$71.25	$71.30
Purchase #7	$118.50	11.669%	$132.3278	$132.33	$132.35	$132.30
7 purchase totals =	$1,068.01		$1,160.6678	$1,160.66	$1,160.70	$1,160.70