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	$205.50	8.694%	$223.3662	$223.37	$223.35	$223.40
Purchase #2	$232.33	6.697%	$247.8891	$247.89	$247.90	$247.90
Purchase #3	$87.59	10.718%	$96.9779	$96.98	$97.00	$97.00
Purchase #4	$153.94	7.550%	$165.5625	$165.56	$165.55	$165.60
Purchase #5	$40.54	12.440%	$45.5832	$45.58	$45.60	$45.60
Purchase #6	$46.89	10.266%	$51.7037	$51.70	$51.70	$51.70
Purchase #7	$162.99	13.480%	$184.9611	$184.96	$184.95	$185.00
7 purchase totals =	$929.78		$1,016.0437	$1,016.04	$1,016.05	$1,016.20