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	$167.67	11.546%	$187.0292	$187.03	$187.05	$187.00
Purchase #2	$160.48	4.262%	$167.3197	$167.32	$167.30	$167.30
Purchase #3	$115.27	7.803%	$124.2645	$124.26	$124.25	$124.30
Purchase #4	$97.66	11.128%	$108.5276	$108.53	$108.55	$108.50
Purchase #5	$40.43	5.790%	$42.7709	$42.77	$42.75	$42.80
Purchase #6	$111.94	10.305%	$123.4754	$123.48	$123.50	$123.50
Purchase #7	$91.70	7.229%	$98.329	$98.33	$98.35	$98.30
7 purchase totals =	$785.15		$851.7163	$851.72	$851.75	$851.70