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	$148.85	4.805%	$156.0022	$156.00	$156.00	$156.00
Purchase #2	$202.65	4.404%	$211.5747	$211.57	$211.55	$211.60
Purchase #3	$222.58	8.288%	$241.0274	$241.03	$241.05	$241.00
Purchase #4	$91.80	12.785%	$103.5366	$103.54	$103.55	$103.50
Purchase #5	$58.87	12.779%	$66.393	$66.39	$66.40	$66.40
Purchase #6	$96.85	12.418%	$108.8768	$108.88	$108.90	$108.90
Purchase #7	$55.84	7.205%	$59.8633	$59.86	$59.85	$59.90
7 purchase totals =	$877.44		$947.2740	$947.27	$947.30	$947.30