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	$53.72	13.591%	$61.0211	$61.02	$61.00	$61.00
Purchase #2	$215.50	6.635%	$229.7984	$229.80	$229.80	$229.80
Purchase #3	$186.60	6.256%	$198.2737	$198.27	$198.25	$198.30
Purchase #4	$150.87	7.785%	$162.6152	$162.62	$162.60	$162.60
Purchase #5	$7.72	10.102%	$8.4999	$8.50	$8.50	$8.50
Purchase #6	$124.82	12.609%	$140.5586	$140.56	$140.55	$140.60
Purchase #7	$194.43	3.104%	$200.4651	$200.47	$200.45	$200.50
7 purchase totals =	$933.66		$1,001.2320	$1,001.24	$1,001.15	$1,001.30