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	$95.94	7.805%	$103.4281	$103.43	$103.45	$103.40
Purchase #2	$14.76	4.298%	$15.3944	$15.39	$15.40	$15.40
Purchase #3	$243.25	12.424%	$273.4714	$273.47	$273.45	$273.50
Purchase #4	$34.31	11.263%	$38.1743	$38.17	$38.15	$38.20
Purchase #5	$67.97	5.844%	$71.9422	$71.94	$71.95	$71.90
Purchase #6	$223.63	7.690%	$240.8271	$240.83	$240.85	$240.80
Purchase #7	$209.91	10.326%	$231.5853	$231.59	$231.60	$231.60
7 purchase totals =	$889.77		$974.8228	$974.82	$974.85	$974.80