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	$196.51	11.514%	$219.1362	$219.14	$219.15	$219.10
Purchase #2	$86.69	11.791%	$96.9116	$96.91	$96.90	$96.90
Purchase #3	$66.36	9.312%	$72.5394	$72.54	$72.55	$72.50
Purchase #4	$30.92	7.746%	$33.3151	$33.32	$33.30	$33.30
Purchase #5	$128.68	13.394%	$145.9154	$145.92	$145.90	$145.90
Purchase #6	$181.77	9.219%	$198.5274	$198.53	$198.55	$198.50
Purchase #7	$130.90	10.277%	$144.3526	$144.35	$144.35	$144.40
7 purchase totals =	$821.83		$910.6977	$910.71	$910.70	$910.60