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	$232.45	9.714%	$255.0302	$255.03	$255.05	$255.00
Purchase #2	$150.98	3.378%	$156.0801	$156.08	$156.10	$156.10
Purchase #3	$52.84	3.183%	$54.5219	$54.52	$54.50	$54.50
Purchase #4	$202.49	9.342%	$221.4066	$221.41	$221.40	$221.40
Purchase #5	$143.56	5.607%	$151.6094	$151.61	$151.60	$151.60
Purchase #6	$37.40	11.143%	$41.5675	$41.57	$41.55	$41.60
Purchase #7	$213.82	7.496%	$229.8479	$229.85	$229.85	$229.80
7 purchase totals =	$1,033.54		$1,110.0636	$1,110.07	$1,110.05	$1,110.00