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	$224.36	7.584%	$241.3755	$241.38	$241.40	$241.40
Purchase #2	$79.30	8.195%	$85.7986	$85.80	$85.80	$85.80
Purchase #3	$82.72	10.369%	$91.2972	$91.30	$91.30	$91.30
Purchase #4	$179.82	9.300%	$196.5433	$196.54	$196.55	$196.50
Purchase #5	$163.74	9.435%	$179.1889	$179.19	$179.20	$179.20
Purchase #6	$218.39	13.727%	$248.3684	$248.37	$248.35	$248.40
Purchase #7	$233.99	3.255%	$241.6064	$241.61	$241.60	$241.60
7 purchase totals =	$1,182.32		$1,284.1783	$1,284.19	$1,284.20	$1,284.20