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	$48.49	9.720%	$53.2032	$53.20	$53.20	$53.20
Purchase #2	$120.77	10.454%	$133.3953	$133.40	$133.40	$133.40
Purchase #3	$63.66	13.503%	$72.256	$72.26	$72.25	$72.30
Purchase #4	$179.45	6.336%	$190.82	$190.82	$190.80	$190.80
Purchase #5	$63.90	7.755%	$68.8554	$68.86	$68.85	$68.90
Purchase #6	$116.61	5.682%	$123.2358	$123.24	$123.25	$123.20
Purchase #7	$80.54	9.540%	$88.2235	$88.22	$88.20	$88.20
7 purchase totals =	$673.42		$729.9892	$730.00	$729.95	$730.00