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	$187.93	10.369%	$207.4165	$207.42	$207.40	$207.40
Purchase #2	$49.37	3.425%	$51.0609	$51.06	$51.05	$51.10
Purchase #3	$72.66	8.303%	$78.693	$78.69	$78.70	$78.70
Purchase #4	$13.94	10.451%	$15.3969	$15.40	$15.40	$15.40
Purchase #5	$67.29	3.755%	$69.8167	$69.82	$69.80	$69.80
Purchase #6	$80.55	11.134%	$89.5184	$89.52	$89.50	$89.50
Purchase #7	$138.59	3.152%	$142.9584	$142.96	$142.95	$143.00
7 purchase totals =	$610.33		$654.8608	$654.87	$654.80	$654.90