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	$106.36	5.274%	$111.9694	$111.97	$111.95	$112.00
Purchase #2	$55.54	10.612%	$61.4339	$61.43	$61.45	$61.40
Purchase #3	$238.85	4.249%	$248.9987	$249.00	$249.00	$249.00
Purchase #4	$56.87	4.865%	$59.6367	$59.64	$59.65	$59.60
Purchase #5	$89.84	6.281%	$95.4829	$95.48	$95.50	$95.50
Purchase #6	$88.56	4.161%	$92.245	$92.25	$92.25	$92.20
Purchase #7	$40.29	3.219%	$41.5869	$41.59	$41.60	$41.60
7 purchase totals =	$676.31		$711.3535	$711.36	$711.40	$711.30