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	$175.51	10.253%	$193.505	$193.51	$193.50	$193.50
Purchase #2	$54.38	3.693%	$56.3883	$56.39	$56.40	$56.40
Purchase #3	$213.90	9.259%	$233.705	$233.71	$233.70	$233.70
Purchase #4	$199.29	6.577%	$212.3973	$212.40	$212.40	$212.40
Purchase #5	$127.82	4.151%	$133.1258	$133.13	$133.15	$133.10
Purchase #6	$28.34	12.570%	$31.9023	$31.90	$31.90	$31.90
Purchase #7	$176.27	6.742%	$188.1541	$188.15	$188.15	$188.20
7 purchase totals =	$975.51		$1,049.1778	$1,049.19	$1,049.20	$1,049.20