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	$38.92	12.158%	$43.6519	$43.65	$43.65	$43.70
Purchase #2	$50.82	6.190%	$53.9658	$53.97	$53.95	$54.00
Purchase #3	$102.48	3.166%	$105.7245	$105.72	$105.70	$105.70
Purchase #4	$141.51	13.711%	$160.9124	$160.91	$160.90	$160.90
Purchase #5	$127.39	5.456%	$134.3404	$134.34	$134.35	$134.30
Purchase #6	$95.28	10.765%	$105.5369	$105.54	$105.55	$105.50
Purchase #7	$180.54	13.159%	$204.2973	$204.30	$204.30	$204.30
7 purchase totals =	$736.94		$808.4292	$808.43	$808.40	$808.40