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	$41.36	8.823%	$45.0092	$45.01	$45.00	$45.00
Purchase #2	$127.89	12.402%	$143.7509	$143.75	$143.75	$143.80
Purchase #3	$185.73	7.268%	$199.2289	$199.23	$199.25	$199.20
Purchase #4	$77.36	8.186%	$83.6927	$83.69	$83.70	$83.70
Purchase #5	$168.94	10.653%	$186.9372	$186.94	$186.95	$186.90
Purchase #6	$221.89	11.773%	$248.0131	$248.01	$248.00	$248.00
Purchase #7	$86.52	12.742%	$97.5444	$97.54	$97.55	$97.50
7 purchase totals =	$909.69		$1,004.1764	$1,004.17	$1,004.20	$1,004.10