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	$188.42	3.223%	$194.4928	$194.49	$194.50	$194.50
Purchase #2	$207.44	7.619%	$223.2449	$223.24	$223.25	$223.20
Purchase #3	$157.69	9.632%	$172.8787	$172.88	$172.90	$172.90
Purchase #4	$178.96	5.783%	$189.3093	$189.31	$189.30	$189.30
Purchase #5	$85.76	4.774%	$89.8542	$89.85	$89.85	$89.90
Purchase #6	$21.95	9.593%	$24.0557	$24.06	$24.05	$24.10
Purchase #7	$107.52	4.164%	$111.9971	$112.00	$112.00	$112.00
7 purchase totals =	$947.74		$1,005.8327	$1,005.83	$1,005.85	$1,005.90