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	$240.56	8.625%	$261.3083	$261.31	$261.30	$261.30
Purchase #2	$173.38	12.116%	$194.3867	$194.39	$194.40	$194.40
Purchase #3	$142.63	4.203%	$148.6247	$148.62	$148.60	$148.60
Purchase #4	$116.81	7.428%	$125.4866	$125.49	$125.50	$125.50
Purchase #5	$25.61	8.588%	$27.8094	$27.81	$27.80	$27.80
Purchase #6	$181.92	3.539%	$188.3581	$188.36	$188.35	$188.40
Purchase #7	$66.87	8.483%	$72.5426	$72.54	$72.55	$72.50
7 purchase totals =	$947.78		$1,018.5164	$1,018.52	$1,018.50	$1,018.50