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	$231.92	4.485%	$242.3216	$242.32	$242.30	$242.30
Purchase #2	$222.48	3.201%	$229.6016	$229.60	$229.60	$229.60
Purchase #3	$174.48	3.725%	$180.9794	$180.98	$181.00	$181.00
Purchase #4	$97.25	8.683%	$105.6942	$105.69	$105.70	$105.70
Purchase #5	$196.33	10.712%	$217.3609	$217.36	$217.35	$217.40
Purchase #6	$114.67	11.498%	$127.8548	$127.85	$127.85	$127.90
Purchase #7	$179.32	6.672%	$191.2842	$191.28	$191.30	$191.30
7 purchase totals =	$1,216.45		$1,295.0967	$1,295.08	$1,295.10	$1,295.20