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	$248.33	6.516%	$264.5112	$264.51	$264.50	$264.50
Purchase #2	$92.64	6.544%	$98.7024	$98.70	$98.70	$98.70
Purchase #3	$63.91	13.693%	$72.6612	$72.66	$72.65	$72.70
Purchase #4	$34.48	12.691%	$38.8559	$38.86	$38.85	$38.90
Purchase #5	$167.52	4.348%	$174.8038	$174.80	$174.80	$174.80
Purchase #6	$99.54	12.642%	$112.1238	$112.12	$112.10	$112.10
Purchase #7	$59.71	3.264%	$61.6589	$61.66	$61.65	$61.70
7 purchase totals =	$766.13		$823.3172	$823.31	$823.25	$823.40