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	$97.87	5.565%	$103.3165	$103.32	$103.30	$103.30
Purchase #2	$212.79	4.180%	$221.6846	$221.68	$221.70	$221.70
Purchase #3	$119.50	10.349%	$131.8671	$131.87	$131.85	$131.90
Purchase #4	$198.56	13.649%	$225.6615	$225.66	$225.65	$225.70
Purchase #5	$161.83	12.360%	$181.8322	$181.83	$181.85	$181.80
Purchase #6	$147.62	12.731%	$166.4135	$166.41	$166.40	$166.40
Purchase #7	$78.79	5.177%	$82.869	$82.87	$82.85	$82.90
7 purchase totals =	$1,016.96		$1,113.6444	$1,113.64	$1,113.60	$1,113.70