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	$111.99	10.408%	$123.6459	$123.65	$123.65	$123.60
Purchase #2	$103.87	9.589%	$113.8301	$113.83	$113.85	$113.80
Purchase #3	$163.49	3.527%	$169.2563	$169.26	$169.25	$169.30
Purchase #4	$177.40	7.283%	$190.32	$190.32	$190.30	$190.30
Purchase #5	$223.79	13.546%	$254.1046	$254.10	$254.10	$254.10
Purchase #6	$186.38	5.230%	$196.1277	$196.13	$196.15	$196.10
Purchase #7	$222.28	11.693%	$248.2712	$248.27	$248.25	$248.30
7 purchase totals =	$1,189.20		$1,295.5558	$1,295.56	$1,295.55	$1,295.50