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	$111.98	12.846%	$126.365	$126.37	$126.35	$126.40
Purchase #2	$106.54	12.124%	$119.4569	$119.46	$119.45	$119.50
Purchase #3	$103.32	8.237%	$111.8305	$111.83	$111.85	$111.80
Purchase #4	$215.35	9.833%	$236.5254	$236.53	$236.55	$236.50
Purchase #5	$6.70	7.169%	$7.1803	$7.18	$7.20	$7.20
Purchase #6	$43.84	6.813%	$46.8268	$46.83	$46.85	$46.80
Purchase #7	$79.60	7.840%	$85.8406	$85.84	$85.85	$85.80
7 purchase totals =	$667.33		$734.0255	$734.04	$734.10	$734.00