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	$111.79	10.152%	$123.1389	$123.14	$123.15	$123.10
Purchase #2	$215.40	4.579%	$225.2632	$225.26	$225.25	$225.30
Purchase #3	$45.59	3.652%	$47.2549	$47.25	$47.25	$47.30
Purchase #4	$56.83	8.663%	$61.7532	$61.75	$61.75	$61.80
Purchase #5	$54.34	7.661%	$58.503	$58.50	$58.50	$58.50
Purchase #6	$202.64	10.206%	$223.3214	$223.32	$223.30	$223.30
Purchase #7	$68.32	9.188%	$74.5972	$74.60	$74.60	$74.60
7 purchase totals =	$754.91		$813.8318	$813.82	$813.80	$813.90