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	$68.96	13.576%	$78.322	$78.32	$78.30	$78.30
Purchase #2	$194.40	9.601%	$213.0643	$213.06	$213.05	$213.10
Purchase #3	$47.44	9.434%	$51.9155	$51.92	$51.90	$51.90
Purchase #4	$62.61	5.629%	$66.1343	$66.13	$66.15	$66.10
Purchase #5	$18.88	7.256%	$20.2499	$20.25	$20.25	$20.20
Purchase #6	$181.75	8.106%	$196.4827	$196.48	$196.50	$196.50
Purchase #7	$142.85	11.448%	$159.2035	$159.20	$159.20	$159.20
7 purchase totals =	$716.89		$785.3722	$785.36	$785.35	$785.30