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	$181.39	4.826%	$190.1439	$190.14	$190.15	$190.10
Purchase #2	$127.55	3.340%	$131.8102	$131.81	$131.80	$131.80
Purchase #3	$164.70	12.761%	$185.7174	$185.72	$185.70	$185.70
Purchase #4	$115.83	7.129%	$124.0875	$124.09	$124.10	$124.10
Purchase #5	$181.56	8.421%	$196.8492	$196.85	$196.85	$196.80
Purchase #6	$240.92	9.396%	$263.5568	$263.56	$263.55	$263.60
Purchase #7	$37.72	9.535%	$41.3166	$41.32	$41.30	$41.30
7 purchase totals =	$1,049.67		$1,133.4816	$1,133.49	$1,133.45	$1,133.40