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	$52.72	8.779%	$57.3483	$57.35	$57.35	$57.30
Purchase #2	$51.40	12.405%	$57.7762	$57.78	$57.80	$57.80
Purchase #3	$124.26	11.149%	$138.1137	$138.11	$138.10	$138.10
Purchase #4	$105.53	8.833%	$114.8515	$114.85	$114.85	$114.90
Purchase #5	$247.88	8.354%	$268.5879	$268.59	$268.60	$268.60
Purchase #6	$202.88	4.711%	$212.4377	$212.44	$212.45	$212.40
Purchase #7	$231.27	13.345%	$262.133	$262.13	$262.15	$262.10
7 purchase totals =	$1,015.94		$1,111.2483	$1,111.25	$1,111.30	$1,111.20