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	$226.78	4.338%	$236.6177	$236.62	$236.60	$236.60
Purchase #2	$185.34	7.705%	$199.6204	$199.62	$199.60	$199.60
Purchase #3	$172.77	13.645%	$196.3445	$196.34	$196.35	$196.30
Purchase #4	$70.27	4.793%	$73.638	$73.64	$73.65	$73.60
Purchase #5	$188.95	9.266%	$206.4581	$206.46	$206.45	$206.50
Purchase #6	$38.92	8.743%	$42.3228	$42.32	$42.30	$42.30
Purchase #7	$196.48	5.300%	$206.8934	$206.89	$206.90	$206.90
7 purchase totals =	$1,079.51		$1,161.8949	$1,161.89	$1,161.85	$1,161.80