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	$209.29	10.426%	$231.1106	$231.11	$231.10	$231.10
Purchase #2	$83.99	7.131%	$89.9793	$89.98	$90.00	$90.00
Purchase #3	$213.26	11.810%	$238.446	$238.45	$238.45	$238.40
Purchase #4	$138.69	12.404%	$155.8931	$155.89	$155.90	$155.90
Purchase #5	$144.35	10.818%	$159.9658	$159.97	$159.95	$160.00
Purchase #6	$148.71	5.296%	$156.5857	$156.59	$156.60	$156.60
Purchase #7	$74.47	7.716%	$80.2161	$80.22	$80.20	$80.20
7 purchase totals =	$1,012.76		$1,112.1966	$1,112.21	$1,112.20	$1,112.20