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	$244.70	5.486%	$258.1242	$258.12	$258.10	$258.10
Purchase #2	$128.33	3.792%	$133.1963	$133.20	$133.20	$133.20
Purchase #3	$210.95	4.328%	$220.0799	$220.08	$220.10	$220.10
Purchase #4	$64.48	12.755%	$72.7044	$72.70	$72.70	$72.70
Purchase #5	$59.59	3.723%	$61.8085	$61.81	$61.80	$61.80
Purchase #6	$66.83	8.791%	$72.705	$72.71	$72.70	$72.70
Purchase #7	$174.82	6.713%	$186.5557	$186.56	$186.55	$186.60
7 purchase totals =	$949.70		$1,005.1740	$1,005.18	$1,005.15	$1,005.20