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	$41.63	5.357%	$43.8601	$43.86	$43.85	$43.90
Purchase #2	$103.77	10.209%	$114.3639	$114.36	$114.35	$114.40
Purchase #3	$142.88	11.222%	$158.914	$158.91	$158.90	$158.90
Purchase #4	$228.42	5.155%	$240.1951	$240.20	$240.20	$240.20
Purchase #5	$103.33	4.873%	$108.3653	$108.37	$108.35	$108.40
Purchase #6	$81.87	5.572%	$86.4318	$86.43	$86.45	$86.40
Purchase #7	$207.67	11.326%	$231.1907	$231.19	$231.20	$231.20
7 purchase totals =	$909.57		$983.3209	$983.32	$983.30	$983.40