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	$208.33	10.129%	$229.4317	$229.43	$229.45	$229.40
Purchase #2	$46.92	7.265%	$50.3287	$50.33	$50.35	$50.30
Purchase #3	$62.89	13.697%	$71.504	$71.50	$71.50	$71.50
Purchase #4	$15.42	9.384%	$16.867	$16.87	$16.85	$16.90
Purchase #5	$167.85	4.466%	$175.3462	$175.35	$175.35	$175.30
Purchase #6	$171.63	5.830%	$181.636	$181.64	$181.65	$181.60
Purchase #7	$53.71	10.190%	$59.183	$59.18	$59.20	$59.20
7 purchase totals =	$726.75		$784.2966	$784.30	$784.35	$784.20